SEASON: Sprinkle the chicken with a pinch of salt and pepper on both sides. Heat a large nonstick skillet over medium-high heat with the olive oil.
SEAR: Add the chicken to the skillet and cook for about 3-5 minutes per side or until the chicken is completely cooked through, remove to a plate. If you are planning on serving this with pasta, get the water going and cook the pasta according to package directions.
SAUTE: Preheat the oven on the broiler setting. Add the onions to the oil remaining in the pan. If there isn't any, add in about ½ teaspoon and sauté the onion for 2-3 minutes until they soften, add the garlic and let cook for 30 seconds.
SIMMER: Add the crushed tomatoes, Italian seasoning, red pepper flakes, dried basil, and pesto and stir to combine. When the sauce reaches a simmer, add a ¼ cup of water, lower the heat, cover and allow to simmer for 10-12 minutes or until the sauce thickens a bit. Season with salt and pepper to taste.
BROIL: Nestle the chicken breasts into the sauce and using a spoon, cover the chicken with sauce. Top each breast with a slice of cheese. Place under the broiler for 1-2 minutes or until the cheese gets nice and bubbly and just melts.
ASSEMBLE: Top with chopped parsley or basil ribbons. Serve with pasta or crusty bread and a salad.