Heat the olive oil in a large skillet over medium heat. Add the diced onion and cook until softened. Add the garlic and cook briefly until fragrant.
Add the ground beef and cook, breaking it apart with a spatula, until browned and no longer pink.
Stir in the chili powder, cumin, paprika, oregano, salt, black pepper, and water. Simmer for 2–3 minutes so the seasonings coat the beef and the flavors come together.
Warm the tortillas in a dry skillet or microwave until soft and flexible.
Fill each tortilla with seasoned ground beef and shredded cheese. Add lettuce, tomato, red onion, avocado, salsa, sour cream, cilantro, and a squeeze of lime as desired.
For food safety, cook ground beef to an internal temperature of 160°F (71°C) before serving.