Preheat your oven to 375°F (190°C). Gather all your ingredients.

In a large skillet over medium heat, cook the ground Italian sausage for 5-7 minutes until browned. Add the chopped onion and minced garlic and sauté until the onion is translucent, about 3-4 minutes.

In a mixing bowl, combine the cooked sausage mixture, frozen cheese tortellini, pizza sauce, cheddar cheese soup, half of the pepperoni, and half of the shredded mozzarella cheese. Stir gently to mix.

Transfer the mixture to a greased 9x13 inch baking dish, spreading evenly. Top with remaining mozzarella and pepperoni.

Bake for 25-30 minutes, or until the cheese is bubbly and golden brown.

Remove from oven and let cool for 5 minutes before serving.