2 medium tomatoes, sliced
1 medium zucchini, sliced
1 medium yellow squash, sliced
12 oz raw lean ground beef
1 large onion, finely chopped
2 medium garlic cloves, minced
1 cup canned tomato sauce
2 cups fat-free ricotta cheese
1 large egg yolk
1/2 cup low-fat shredded mozzarella cheese (or Italian cheese blend)
1 tbsp (or slightly more) combo of parsley, oregano and/or rosemary
1/8 tsp table salt, or to taste
1/8 tsp black pepper, or to taste
Chopped fresh basil, optional
Preheat oven to 500ºF. Coat a baking sheet with cooking spray and spread tomato, zucchini and squash slices over sheet. Roast vegetables for 10 to 12 minutes.
Meanhwile, in a large, nonstick skillet, sauté beef, onion and garlic until beef is browned. Stir in tomato sauce and bring to a simmer.
Spread beef mixture in a large, shallow baking dish (3 quart or 9 X 13-inches) and top with roasted vegetables. Reduce oven temperature to 350ºF.
Whisk together ricotta cheese, egg yolk, mozzarella cheese, herbs, salt and pepper in a medium bowl. Spoon over roasted vegetables and smooth with a rubber spatula.
Bake until very hot and bubbling around edges, about 35 minutes. Cut into six equal pieces and serve immediately. (Note: If preparing casserole in advance and freezing it, make sure to thaw it completely in the refrigerator before baking it. Increase the baking time by 5 to 10 minutes.)