If your chicken breasts are thick on one end, place them between two sheets of plastic wrap and pound the thicker end gently with a meat mallet until the breast is an even 3/4-inch thickness throughout. This helps them cook evenly without the thin end drying out. Pat dry and season both sides with salt and pepper.

Heat the olive oil in a 12-inch skillet over medium-high heat until shimmering. Add the chicken breasts in a single layer and cook without moving them for 5 to 6 minutes. The bottom should be deep golden brown and the edges white and opaque about halfway up. Flip and cook another 4 to 5 minutes until the internal temperature reaches 165 degrees F. Transfer to a clean plate.

Reduce the heat to medium. Add the sliced garlic and red pepper flakes to the same pan and cook for about 30 seconds, stirring, until fragrant but not browned. Add the cherry tomatoes. Let them sit for 1 minute, then stir. Cook for 3 to 4 minutes, stirring occasionally, until the skins blister and most of the tomatoes have burst and released their juices into the pan.

Remove the skillet from the heat or reduce to the lowest setting. Spoon the pesto over each chicken breast directly on the plate, using about 1 tablespoon per piece. You can also spoon pesto right into the tomato juices in the pan and stir gently to combine them into a loose sauce. Adding pesto off high heat keeps that bright, fresh flavor intact.

Return the chicken to the pan and spoon the tomato-pesto mixture over the top of each piece. Let everything rest together for 2 minutes so the flavors come together. Scatter torn fresh basil over the top and finish with Parmesan if desired. Serve immediately over pasta, polenta, or with crusty bread to soak up the sauce.