In a small bowl, mix together chili powder, cumin, smoked paprika, garlic powder, onion powder, oregano, cayenne (if using), salt, and black pepper. Set aside.
Heat a large skillet over medium-high heat. If using lean beef (90/10 or leaner), add 1 tablespoon oil. Add the ground beef and cook, breaking it up with a wooden spoon, until no longer pink and an instant-read thermometer inserted into the thickest part registers 160°F (71°C), about 5-7 minutes.
Carefully drain any excess fat from the skillet, leaving about 1 tablespoon. Return skillet to heat, sprinkle the seasoning blend evenly over the beef, and pour in the water or broth. Stir well to combine and bring to a simmer. Cook, stirring occasionally, for 5-7 minutes until the liquid is mostly absorbed and the beef is deeply coated. Taste and adjust salt.
While the beef simmers, warm tortillas in a dry skillet over medium heat for about 30 seconds per side, or wrap in a damp paper towel and microwave for 20-30 seconds. Keep them wrapped in a clean kitchen towel to stay warm.
Spoon the seasoned beef into the center of each warm tortilla. Top generously with lettuce, tomato, cheese, cilantro, and a drizzle of sour cream. Serve immediately with lime wedges on the side.