Judith Winfrey’s Yellow Squash with Tomatoes and Parmesan

Preheat oven to 400 degrees. Heat olive oil in a medium ovenproof skillet over medium-low heat. Add onions and cook slowly for 15 to 20 minutes to caramelize them. Remove from heat; top onions with an even layer of squash slices, then with tomato slices. Season to taste with salt and pepper; sprinkle with cheese. Place in the oven and bake for 20 to 30 minutes, just until the squash is tender but not mushy.