Add 3 cups uncooked spiral pasta to a pot of boiling water and cook according to package instructions. Cook al dente, then drain and set aside.
In a large pot over medium-high heat, cook 1 lb lean ground beef and 1 cup chopped yellow onion until beef is browned and onion turns translucent. Fold a paper towel and swish it around using a spatula to absorb any excess grease.
Now add 24 oz pasta sauce, 14 oz drained diced tomatoes, 2 cups sliced mushrooms, 1 teaspoon dried oregano, ½ teaspoon garlic powder, ½ teaspoon salt and ¼ teaspoon ground black pepper to the pot and stir everything together. Bring to a boil, then reduce heat to let simmer for 5 minutes.
Remove the pot from heat then add the cooked pasta noodles. Stir everything together.
Pour the mixture into a 9×11 casserole dish and spread evenly with a spatula. Sprinkle 1 cup shredded cheddar cheese over top, then sprinkle 1 cup shredded mozzarella cheese.
Bake uncovered for 25-30 minutes or until the cheese is melted and bubbly. Let cool for 5 minutes then scoop onto plates and serve.