Preheat oven to 350°F (180°C).

Spray an 8 x 8-inch casserole dish with vegetable cooking spray or grease with olive oil.

Cook pasta until al dente, drain, and cool.

Thinly slice the yellow onion.

Crush the garlic cloves.

In a skillet, saute onion and garlic in a little olive oil until softened.

In a large bowl, combine cooked pasta, sauteed onion and garlic, chopped basil, chopped Italian parsley, salt, pepper, Parmesan cheese (reserve a little for topping), ricotta cheese, and beaten egg.

Toss all ingredients together well.

Spread half of the pasta mixture in the prepared casserole dish and press down gently.

Layer with half of the sliced tomato and zucchini.

Sprinkle with half of the remaining Parmesan and mozzarella cheese.

Repeat the pasta mixture, tomato, zucchini, and cheese layers.

Cover the dish with foil.

Bake for 35 minutes.

Remove the foil and bake for another 5 to 10 minutes, or until the cheese is melted, bubbly, and lightly golden brown.

Let cool for 5 to 10 minutes before cutting into squares and serving.