Preheat oven to 375°F (190°C).

In a large skillet, heat olive oil over medium heat. Sauté onions and garlic until translucent.

Add ground beef; cook until browned. Drain excess fat.

Stir in crushed tomatoes, Italian seasoning, salt, and pepper. Simmer for 15-20 minutes.

Cook ziti according to package instructions until al dente; drain.

In a baking dish, layer half of the meat sauce followed by half of the cooked ziti and dollops of ricotta cheese. Repeat layers.

Top with remaining meat sauce and sprinkle with mozzarella cheese.

Cover with foil and bake for 20 minutes; remove foil and bake for an additional 10-15 minutes until bubbly.