Heat a grill pan to medium-high heat. Whisk together the olive oil, lemon juice, garlic, red pepper flakes, and season with salt and pepper. Add the marinade to a zip-top bag and add the chicken. Adjust the chicken pieces so they are all coated with the marinade. Let sit out at room temperature for 10 to 15 minutes while you make the sauce. Grill the chicken for 3 to 4 minutes on each side. Add a ladleful of Basic Tomato Sauce to an 8- by 8-inch casserole dish. Place the chicken in the casserole dish, shingling slightly, and ladle some sauce on top. Sprinkle with the mozzarella and Parmesan. Broil until golden and bubbly, about 5 minutes Basic Tomato Sauce: Add the tomatoes to a blender and puree until smooth. Heat the olive oil in a large saucepan over medium-high heat. Once hot, add the onions and saute until tender, about 5 minutes. Stir in the garlic and red pepper flakes and cook until the garlic is fragrant, about 1 minute. Add the tomatoes, bring to a boil, reduce the heat to a simmer and cook for 20 minutes. Stir in the basil the last minute of cooking.