pasta primavera recipe

12 oz pasta (penne, fettuccine, or your favorite type) - 2 tablespoons olive oil - 1 small onion, chopped - 3 cloves garlic, minced - 1 cup cherry tomatoes, halved - 1 bell pepper (red, yellow, or green), sliced - 1 zucchini, sliced - 1 yellow squash, sliced - 1 cup broccoli florets - 1 cup snap peas - 1 cup baby spinach - 1/2 cup grated Parmesan cheese - 1/4 cup fresh basil, chopped - Salt and black pepper to taste - Red pepper flakes (optional, for a bit of heat) - Juice of 1 lemon