Preheat the oven to 375℉. Spray a 2-quart casserole dish with nonstick spray.
In a large skillet, heat the olive oil over medium heat. Add the onion, zucchini, garlic, and red pepper flakes. Cook, stirring, until the vegetables are softened, about 5 minutes. Remove the vegetables to a bowl and set aside.
Add the beef to the pan and cook, breaking it apart with a spatula, until browned, about 8 to 10 minutes. Drain off any accumulated oil and discard.
Add the cooked vegetables, penne, and sauce to the pan and mix to combine. Spoon the pasta mixture into the prepared casserole dish. Sprinkle with cheese.
Bake until the cheese is melted and the filling is hot and bubbly, about 20 to 25 minutes. Sprinkle fresh basil on top and serve.
