In a skillet over medium heat, cook the turkey until evenly brown. Drain and set aside. Heat oil in the skillet, and cook garlic, onion, yellow squash/zucchini, and spinach until tender. Return turkey to the skillet. Mix in the tomatoes and tomato paste, and season with Italian seasoning, cayenne, salt, and pepper. Stuff the green/yellow/red peppers with the skillet mixture. Scoop 1 Tbsp ricotta cheese in the middle.