Wash basil, chop. Fill a large pot with water and a dash of salt. Bring to a boil. Cook pasta for 8-10 minutes. Reserve 1 C. of pasta water. Drain. Rinse. Wash and cut tomatoes in half. In a skillet on medium high heat add 1 T. of oil and cook chicken for 5-7 minutes, until done. Remove. Dice. In a large skillet on medium heat add 1T. of oil and the onions. Sauté for 3-4 min. Add the squash and tomatoes. Season with salt and pepper. Sauté for 3-4 minutes. Add the reserved pasta water, pasta, and chicken. Stir until combined. Sprinkle the grated Parmesan cheese over the pasta. Stir. Dollop the Ricotta cheese over pasta and top with basil.
