1. Bring a large pot of salted water to a boil. Cook pasta shells until al dente, about 9–10 minutes. Drain and rinse with cool water. Set aside.

2. In a skillet over medium heat, heat olive oil and sauté onions until softened. Add ground beef and cook until browned. Drain any excess grease.

3. Stir in garlic, taco seasoning, and water. Let it simmer for 2–3 minutes. Remove from heat and allow to cool slightly.

4. In a bowl, mix together the cooked taco meat, 3/4 cup shredded cheese, ricotta (or cottage cheese), and half of the salsa. Add cumin, salt, and pepper.

5. Preheat oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish and spread a layer of diced tomatoes and tomato sauce on the bottom.

6. Fill each shell with the taco mixture and place open side up in the baking dish.

7. Spoon remaining salsa over the shells and sprinkle with the remaining cheese. Cover with foil and bake for 20 minutes.

8. Uncover and bake an additional 10–15 minutes until cheese is melted and bubbly.

9. Rest for 5 minutes before serving. Garnish with cilantro or parsley and serve with sour cream if desired.