Preheat oven to 375 degrees. Coat a 9 x 9-inch baking dish with cooking spray. Set aside.
Cook tortellini according to package instructions. Drain. Set aside.
To make cheese sauce: In a large nonstick pan, melt butter. Using a whisk, mix in dry mustard powder, garlic powder, and cayenne pepper, if desired. Whisk in milk, ricotta cheese, and 1 cup shredded cheese. Season to taste with a little salt and pepper.
Using a rubber spatula so the tortellini doesn’t tear, stir in cooked tortellini and tomatoes. Mix well. Add to baking dish and spread evenly. Sprinkle with ¼ cup shredded cheese and the Parmesan cheese all over top of casserole. Bake in oven for about 15 minutes, until the cheeses are melted.
Cool slightly and cut into 6 servings. This casserole freezes great.