Preheat your oven to 375°F and grease a 9x13 casserole dish.

Boil the rotini al dente according to package directions. Drain and set aside.

In a large skillet over medium-high heat, fry the ground beef with the diced sweet onion until browned. Season with salt and pepper. Drain excess grease.

Stir the cottage cheese into the hamburger and onion mixture until well combined.

Pour the pasta sauce over the meat mixture and stir to coat.

Add the cooked rotini to the skillet and stir everything together.

Transfer to the prepared casserole dish and spread evenly. Top with shredded mozzarella.

Bake for 20-25 minutes until cheese is melted and bubbly. Let cool 5 minutes before serving.