Preheat Oven: Set your oven to 350°F. Grease a 9×13-inch baking dish and set aside.

Cook Mushrooms: In a large, deep skillet over medium-high heat, add the mushrooms to the dry skillet. Stir occasionally until they’re soft, slightly browned, and most of their liquid has evaporated, about 5-8 minutes. Transfer mushrooms to a bowl and set aside.

Sauté Vegetables: In the same skillet, heat 1 tablespoon of oil. Add the chopped onion, garlic, and bell pepper. Sprinkle with a pinch of salt. Cook, stirring occasionally, until the vegetables are softened, about 5 minutes.

Brown Beef: Add the ground beef to the skillet with the vegetables. Cook, breaking up the meat with a spoon, until it’s browned and no longer pink. Drain excess fat if necessary.

Add Tomatoes and Seasonings: Stir in the canned tomatoes with their juice, breaking up the tomatoes with a spoon. Add the tomato paste, oregano, crushed red pepper flakes, and freshly ground black pepper. Let the mixture simmer for about 10 minutes to blend the flavors.

Cook Pasta: While the sauce simmers, bring a large pot of salted water to a boil. Add the elbow macaroni and cook until just al dente, according to package instructions. Drain and set aside.

Combine Ingredients: In a large mixing bowl, combine the cooked pasta, meat and vegetable sauce, and the cooked mushrooms. Stir in half of the grated cheddar and half of the Parmesan cheese.

Assemble Casserole: Transfer the mixture into the prepared baking dish. Sprinkle the remaining cheddar and Parmesan cheeses evenly over the top.

Bake: Place the casserole in the preheated oven and bake until the cheese is melted and bubbly, about 30 minutes.

Serve: Remove from the oven and let it rest for a few minutes before serving. Enjoy!