Slice zucchini very thin, and combine with diced onion in a lightly greased (butter or olive oil) saute pan. While cooking, season with salt, pepper, oregano, and minced garlic, all to taste. You may use garlic powder if you prefer.
When zucchini is soft, add tomato sauce, pinch of sugar, and parmesan cheese. Stir together and simmer for approximately 10 minutes.
Add swiss or mozzarella on top, your choice. You may use sliced cheese or grated cheese, whatever is handy.