Roast Tomatoes:

• Preheat your oven to 400°F (200°C).
• On a rimmed baking sheet, toss the grape or cherry tomatoes with 2 tablespoons of the olive oil, salt, and pepper. Spread the tomatoes in a single layer.
• Roast for about 20 minutes, or until the tomatoes are blistered and slightly softened.

Prepare and Cook Chicken:

• While the tomatoes are roasting, prepare the chicken. If the chicken breasts are very thick, pound them to a more even thickness. Pat the chicken dry with paper towels.
• Season the chicken breasts generously on all sides with garlic powder, paprika, salt, and pepper.
• Heat the remaining 2 tablespoons of olive oil in a large skillet over medium heat.
• Add the seasoned chicken breasts to the hot skillet. Cook for about 5 minutes per side, or until golden brown and cooked through (internal temperature reaches 165°F/74°C).
• Remove the cooked chicken from the skillet and set aside on a plate.

Sauté Aromatics:

• In the same skillet (do not clean), add the chopped onion. Sauté over medium heat until softened and lightly caramelized, about 3-4 minutes. Add a little more oil if the pan is too dry.
• Add the minced garlic and cook for about 30 seconds more, stirring constantly, until fragrant.

Make Creamy Pesto Sauce:

• Add the basil pesto to the skillet and stir quickly to combine with the onion and garlic.
• Pour in the heavy whipping cream and add the grated Parmesan cheese. Stir gently.
• Bring the sauce to a gentle simmer, stirring until the Parmesan is melted and the sauce is smooth.

Combine and Finish:

• Return the cooked chicken breasts to the skillet with the sauce.
• Add the roasted tomatoes (and any juices from the baking sheet) to the skillet.
• Stir gently to coat the chicken and tomatoes in the sauce. Reheat for a couple of minutes until everything is warmed through. Add red pepper flakes, if using.

Serve: Serve the creamy pesto chicken with roasted tomatoes immediately. Garnish with fresh basil or parsley, if desired.