01 - Preheat oven to 350°F.
02 - In a large skillet over medium heat, cook the ground beef, breaking it apart with a spoon, until browned, about 5 minutes. Drain excess fat if needed.
03 - Add chopped onion and garlic to the skillet. Sauté for 2–3 minutes until softened.
04 - Stir in tomato paste, chili powder, cumin, paprika, oregano, salt, and pepper. Cook for 1 minute to bloom the spices.
05 - Add water, reduce heat, and simmer for 3–4 minutes until the mixture thickens. Remove from heat.
06 - Arrange taco shells on a baking sheet. Sprinkle a small amount of cheese in the bottom of each shell. Bake for 3–4 minutes until shells are warmed through and cheese is melted.
07 - Fill each shell with the beef mixture, then top with lettuce, diced tomatoes, remaining cheese, and any desired toppings.
08 - Serve immediately with sour cream and salsa on the side.