It's Friday, October 24th, and the air here in Casablanca is finally carrying that first, unmistakable promise of coole, cozy weather. It's the time of year that always makes me nostalgic for my home kitchen in Austin and the iconic, comforting bakes of the holiday season. At the top of that list, always, is my Grandma's Sweet Potato Butter Cake. This isn't just a cake; it's a treasure. It's an old-fashioned, incredibly moist, and velvety cake that uses the magic of mashed sweet potato and sour cream to create a crumb that is just impossibly tender. This is the perfect, simple, one-layer cake for a Thanksgiving table or just a cozy fall afternoon.
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My grandma's secret, which I swear by: Use truly softened butter and room temperature eggs and sour cream. When I once rushed this with cold ingredients, the cake was dense. Letting them come to room temperature is the non-negotiable step for achieving that light, fluffy, perfect "butter cake" texture.
The Ultimate "Pound Cake" Style Fall Loaf
This recipe is a Southern classic, and for good reason. It's essentially a perfect pound cake, but with the added moisture, beautiful golden colour, and subtle, earthy sweetness of sweet potatoes. It's not overly spiced-just a gentle warmth from cinnamon and nutmeg-which really lets the rich, buttery, sweet-potato flavour shine. It's dense in the most wonderful way: plush, velvety, and melts in your mouth. The optional buttery glaze is just the cherry on top.
Why You'll Love This Recipe
- Incredibly Moist & Tender: The combination of sweet potato, sour cream, and the "creaming method" creates a famously moist, velvety crumb that stays fresh for days.
- Rich, Buttery Flavour: This is a true "butter cake," with a rich flavour that is perfectly complemented by the earthy, sweet potato.
- Simple & Classic: No complex layers or techniques. Just a straightforward, one-pan cake that delivers perfect, comforting results every time.
- The Perfect Holiday Cake: It's an ideal make-ahead dessert for Thanksgiving or Christmas. It travels well and is a total crowd-pleaser.
Ingredients
Here's what you'll need for this classic Southern-style cake. For the full list with precise measurements, see the recipe card at the end of the post!
For the Sweet Potato Cake
- Butter: 1 cup (2 sticks) of unsalted butter, softened to room temperature.
- Sugar: Granulated sugar.
- Eggs: 4 large eggs, also at room temperature.
- Sweet Potato: 1 cup of mashed sweet potatoes. You can use canned 100% pure pumpkin puree, but I find homemade (roasted or boiled) mashed sweet potato has the best flavour.
- Dairy: Full-fat sour cream and whole or 2% milk, both at room temperature.
- Flavour: Pure vanilla extract.
- Flour: All-purpose flour, spooned and leveled.
- Leavening: Baking powder and baking soda.
- Spices: A classic, warm blend of ground cinnamon and ground nutmeg, plus salt to balance the sweetness.
For the Optional Glaze
- Unsalted Butter: Melted.
- Powdered Sugar: Sifted, to prevent lumps.
- Milk & Vanilla Extract
How to Make Grandma's Sweet Potato Butter Cake
This is a classic "creaming method" cake. The most important part is using room temperature ingredients for a light, fluffy batter.
Step 1: Preheat and Prep the Pan
First, I preheat my oven to 350°F (175°C). This recipe is versatile: you can use a 9×13-inch baking dish (for a one-layer sheet cake) or a 10- or 12-cup Bundt pan (for a showstopper). Whichever I choose, I grease and flour it very thoroughly.
Step 2: Cream Butter, Sugar, and Eggs
In a large bowl (or the bowl of a stand mixer fitted with the paddle attachment), I add the softened butter and granulated sugar. I beat them together on medium-high speed for a full 3-4 minutes. The mixture should become visibly pale, light, and fluffy. This is the most important step for the cake's light texture.
I scrape down the sides of the bowl, then add the room-temperature eggs one at a time, mixing well on medium speed after each one until it's fully incorporated.
Step 3: Add Wet Ingredients
Next, I add the mashed sweet potatoes, room-temperature sour cream, milk, and vanilla extract to the bowl. I mix on low speed until everything is smooth and well combined. The batter will be a beautiful pale orange.
Step 4: Combine Dry Ingredients
In a separate medium bowl, I whisk together the all-purpose flour, baking powder, baking soda, salt, cinnamon, and nutmeg.
Step 5: Mix the Batter and Bake
I gradually add the dry ingredients to the wet ingredients, mixing on low speed just until the flour streaks disappear. Do not overmix! Overmixing will make the cake tough.
I pour the batter into my prepared pan and smooth the top with a spatula.
- For a 9x13-inch pan, I bake for 40-45 minutes.
- For a Bundt pan, I bake for 50-60 minutes.
The cake is done when it's golden brown and a wooden skewer or toothpick inserted into the center comes out clean.
Step 6: Cool and Glaze
I let the cake cool in the pan on a wire rack for 15 minutes. After 15 minutes, I carefully invert the loaf onto the wire rack to cool completely.
If I'm using the glaze, I wait until the cake is completely cool. In a small bowl, I whisk the melted butter, powdered sugar, milk, and vanilla until smooth. I drizzle this all over the top of the cooled cake.
Common Mistakes to Avoid
- Using Cold Ingredients: This is the #1 mistake. If your butter, eggs, and sour cream are cold, they won't emulsify. The batter will look curdled and will bake into a dense, heavy, or greasy cake.
- Overmixing the Flour: Once the flour goes in, your goal is to mix as little as possible. As soon as the dry streaks are gone, stop. This is the secret to a tender, "pound-cake" style crumb.
- Using Pumpkin Pie Filling: If you substitute pumpkin for sweet potato, make sure it's 100% pure pumpkin puree, not canned pumpkin pie filling, which is pre-sweetened and spiced.
Tips and Tricks for Success
- Room Temp is Key: I'll say it again. Set your butter, eggs, sour cream, and milk on the counter for at least 1-2 hours before you begin. This is the secret to a fluffy, fine-grained butter cake.
- How to Mash Sweet Potatoes: The easiest way is to bake 1-2 large sweet potatoes at 400°F (200°C) for 45-60 minutes until they are totally soft. Let them cool, peel, and mash the flesh until perfectly smooth.
- Grease & Flour That Pan!: This is a very moist, rich cake. It will stick, especially in a Bundt pan with intricate crevices. Grease the pan with butter or shortening, then dust it with flour, tapping out any excess.
- The Creaming Method: The act of beating butter and sugar for 3-5 minutes until "pale and fluffy" is a physical leavening step. It forces air into the fat, creating tiny bubbles that, when combined with leaveners, result in a fine, tender crumb. Don't rush this step!
Variations
This cake is a stunning base for other fall flavours!
- Add a Streusel: Before baking, sprinkle the 9x13 version with a cinnamon-pecan streusel (½ cup flour, ¼ cup brown sugar, ¼ cup chopped pecans, 2 tablespoon cold butter).
- Add Nuts: Fold 1 cup of chopped, toasted pecans or walnuts into the batter with the last addition of flour.
- Add a Kick: Add 1-2 tablespoons of bourbon or dark rum to the batter along with the vanilla.
- Cream Cheese Frosting: Instead of the glaze, top the cooled cake (9x13 version) with a classic cream cheese frosting.
How to Serve
This Sweet Potato Butter Cake is a perfect, elegant dessert or coffee cake.
- It is fantastic served at room temperature with its simple vanilla glaze.
- It's the perfect, crowd-pleasing dessert to bring to a Thanksgiving or Christmas gathering.
- I also love serving a slice slightly warmed (15 seconds in the microwave) with a cup of hot coffee for a cozy fall breakfast.
Make Ahead and Storage
This cake is an excellent make-ahead bake, as the flavour and moisture are even better on day two!
- Make Ahead: Bake the cake 1-2 days in advance.
- Storage: Store the completely cooled cake (un-glazed or glazed) in an airtight cake carrier (or tightly covered with plastic wrap) at room temperature for up to 4 days.
- Freezing: This cake freezes beautifully! I recommend freezing the loaf before glazing. Wrap the cooled loaf tightly in plastic wrap, then a layer of aluminum foil. Freeze for up to 3 months. Thaw overnight at room temperature and glaze before serving.
Recipe Notes / What I Learned
This recipe is a beloved hand-me-down, and the original instructions were just "a can of sweet potatoes" and "a lump of butter." Through testing, I've found that using freshly roasted and mashed sweet potatoes gives a much deeper, more authentic, caramelized flavour than canned puree. However, in a pinch, 1 cup of canned 100% pure sweet potato puree (patted dry with a paper towel if it looks watery) will absolutely work.
Nutrition Snapshot
Estimated Nutrition Per Serving (1/16th of 9x13 cake): ~320 calories · 5g protein · 44g carbs · 14g fat (This is an approximation and can vary based on the exact size of your sweet potatoes.)
Grandma's Famous Sweet Potato Butter Cake
Equipment
- 9x13-inch baking dish or Bundt pan
- Large bowl
- Electric mixer
- Separate bowl (for dry ingredients)
- Whisk
- Spatula
- Wire rack
- Small saucepan for glaze
Ingredients
Group: For the Cake
- 1 cup (2 sticks) unsalted butter softened
- 1½ cups granulated sugar
- 4 large eggs
- 1 cup mashed sweet potatoes about 1 large cooked and peeled sweet potato
- ½ cup sour cream room temperature
- ¼ cup milk whole or 2%
- 2 teaspoons vanilla extract
- 2 cups all-purpose flour
- 2 teaspoons baking powder
- ½ teaspoon baking soda
- ½ teaspoon salt
- 1 teaspoon ground cinnamon
- ¼ teaspoon ground nutmeg
Group: Optional Glaze
- 4 tablespoons (½ stick) unsalted butter melted
- ½ cup powdered sugar
- 1-2 tablespoons milk
- ½ teaspoon vanilla extract
Instructions
- Preheat oven to 350°F (175°C). Grease and flour a 9×13-inch baking dish or bundt pan.
- In a large bowl, beat softened butter and sugar together until light and fluffy, about 2-3 minutes. Scrape sides as needed.
- Add eggs one at a time, mixing well after each addition.
- Stir in mashed sweet potatoes, sour cream, milk, and vanilla extract until smooth.
- In a separate bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, and nutmeg.
- Gradually add dry ingredients to wet ingredients, stirring gently until just combined. Avoid overmixing.
- Pour batter into prepared pan and smooth top with a spatula.
- Bake in a 9×13-inch pan for 40-45 minutes or in a bundt pan for 50-60 minutes, until a toothpick inserted in the center comes out clean.
- Let cake cool in pan for 15 minutes, then transfer to wire rack to cool completely.
- For the glaze (optional), melt butter in a small saucepan. Whisk in powdered sugar, milk, and vanilla extract until smooth. Drizzle over cooled cake.
- Slice and serve.
Notes
Nutrition
FAQs
Can I use pumpkin puree instead of sweet potato?
Yes, 1 cup of 100% pure pumpkin puree (not pie filling) is an excellent 1-to-1 substitute and will make a delicious Pumpkin Butter Cake.
Can I make this dairy-free?
Yes. Use a high-quality plant-based butter stick (like Miyoko's Kitchen), a plant-based sour cream (like Kite Hill), and an unsweetened plant-based milk (like oat or almond).
Can I make this in a different pan?
Yes! This recipe is very versatile. As noted, it works in a 9x13 inch pan (bake 40-45 mins) or a 10-12 cup Bundt pan (bake 50-60 mins). It also makes 24 standard-sized cupcakes (bake 18-22 mins).
