1. Preheat your oven to 375°F and place taco shells on a baking sheet. Warm for 5 minutes to restore crispness.

2. In a large skillet over medium heat, cook the ground beef until fully browned, breaking it up with a spatula as it cooks.

3. Drain any excess fat from the skillet, then return it to medium heat.

4. Stir in the chili powder, cumin, paprika, garlic powder, onion powder, oregano, salt, and sugar.

5. Add the tomato paste and water. Stir well to coat the beef evenly in the sauce.

6. Let the mixture simmer for 5 minutes, stirring occasionally, until slightly thickened and glossy.

7. To assemble, layer lettuce in the bottom of each taco shell, followed by guacamole or avocado, then spoon in the beef mixture.

8. Top with diced tomatoes, red onion, and shredded cheese.

9. Garnish with cilantro and a squeeze of lime, if desired. Serve immediately.