Baking pasta with cheese on top creates a chewy and crispy topping kids will love. You can assemble the dish ahead and refrigerate it, then bake it right before dinner. Try this recipe with 1 pound of spaghetti (cook a few minutes less than the package instructions direct). Don't worry if it seems like there's too much sauce; it will be absorbed as the pasta bakes.
Preheat oven to 425 degrees. Heat oil in a large saucepan over medium heat. Add onion and garlic, and season with salt and pepper; cook, stirring occasionally, until softened, about 5 minutes. Add thyme and tomatoes. Bring to a boil, reduce heat, and simmer, breaking up tomatoes with spoon, until sauce is thickened and reduced to about 5 1/2 cups, 20 to 25 minutes.
Meanwhile, cook ravioli in a large pot of boiling salted water just until they float to the top (pasta will continue to cook in oven). Drain pasta; return to pot.
Toss sauce with pasta. Pour pasta into a large gratin dish or 9-by-13-inch baking dish, and sprinkle with cheeses. Bake until golden, 20 to 25 minutes. Cool slightly before serving.