Zucchini-Tomato Skillet

1 onion, chopped

ˆ½ cup butter, melted

4 medium zucchini (about 1ˆ½ pounds), sliced

ˆ½ pound fresh mushrooms, sliced

3 medium tomatoes (about 1 pound), sliced

3 tablespoons fresh parsley, chopped

ˆ½ cup parmesan cheese, grated

1 teaspoons fresh basil, chopped (or teaspoon dried)

ˆ½ teaspoon salt

ˆ½ teaspoon pepper