How To Make Pasta al Forno:

1. In a large pot or dutch oven, heat olive oil over medium heat. Add onion and sauté for 3-4 minutes, then add garlic and cook for 1 more minute.
2. Add sausage and break into small crumbles with a spatula. Cook until browned, then drain off grease.
3. Add tomato puree, ¼ cup water, salt, pepper, and oregano. Reduce heat and simmer for 30 minutes.
4. As sauce simmers, boil pasta in generously salted water until almost al dente (slightly undercooked). Measure out 1 cup of the pasta water and set aside, then drain out the remaining water.
5. Add the cooked pasta to the sauce after the 30 minutes, along with 1 ½ cups mozzarella and ½ cup pasta water. Stir to combine and add remaining pasta water only if the mixture is dry.
6. Preheat oven to 350 degrees F.
7. Transfer pasta mixture to a 9×13-inch baking dish and top with remaining mozzarella and parmesan.
8. Bake pasta for 25-30 minutes or until bubbling and cheese begins to turn golden.