Cook ground beef and onion in a skillet over medium-high heat for 5-7 minutes, breaking up meat, then add garlic and cook 30 seconds. Drain excess fat if needed.

Stir in chili powder, cumin, paprika, and salt; cook 30 seconds. Add water, bring to a simmer, then cook over low heat 2-3 minutes until thickened.

While beef cooks, wash and dry lettuce leaves. Dice tomato and avocado, chop cilantro. Set out sour cream and cheese.

Fill lettuce cups with beef, then top with tomato, avocado, sour cream, cheese, and cilantro. Serve with lime wedges immediately.