Step 1: Heat olive oil in a large skillet over medium-high heat. Add the ground beef and cook, breaking it up with a spoon, until browned. Drain any excess fat.
Step 2: Stir in the chili powder, ground cumin, garlic powder, onion powder, cayenne pepper (if using), salt, and black pepper. Cook for 1 minute, stirring constantly, until fragrant.
Step 3: Pour in the water and bring to a simmer. Reduce heat to low, cover, and let it cook for 5-7 minutes, allowing the flavors to meld and the sauce to thicken slightly.
Step 4: While the meat simmers, prepare your taco toppings: shred lettuce, dice tomatoes, shred cheese, and chop cilantro. Warm taco shells according to package directions (oven, microwave, or skillet).
Step 5: To assemble, fill each warm taco shell with a generous spoonful of seasoned beef. Top with shredded lettuce, diced tomatoes, shredded cheese, a dollop of sour cream, and fresh cilantro.
Step 6: Serve immediately with lime wedges on the side.