Preheat Oven & Prepare Pan: Preheat oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.
Make the Sauce: Heat olive oil in a large saucepan over medium heat. Add onion and cook until softened, about 5 minutes. Add garlic and cook for 1 minute. Add ground beef and cook, breaking it up with a spoon, until browned. Drain any excess grease.
Simmer Sauce: Stir in crushed tomatoes, tomato sauce, tomato paste, oregano, basil, salt, and pepper. Bring to a simmer and cook for 15 minutes, stirring occasionally.
Layer Lasagna: Spread a thin layer of sauce in the prepared baking dish. Top with a layer of lasagna noodles, overlapping as needed. Spread with another layer of sauce, then sprinkle with mozzarella cheese. Repeat layers.
Bake: Cover the lasagna with foil and bake for 30 minutes. Remove foil and bake for an additional 10 minutes, or until the cheese is melted and bubbly.
Rest & Serve: Let the lasagna rest for 10 minutes before slicing and serving.