01 - Heat a large skillet over medium heat. Add the ground beef and cook for 3–4 minutes, breaking it up with a spoon, until it starts to brown.
02 - Add the chopped onion and cook for another 3 minutes, until softened. Stir in the garlic and cook for 1 minute until fragrant.
03 - Add the tomato paste, chili powder, cumin, smoked paprika, oregano, salt, and black pepper. Cook, stirring constantly, for 1 minute to toast the spices and release their flavors.
04 - Pour in the water, stir well to combine, and simmer uncovered for 5 minutes until most of the liquid has evaporated and the beef mixture has thickened nicely.
05 - While the beef simmers, warm the hard taco shells according to package instructions, typically 2–3 minutes in a preheated oven at 350°F.
06 - Spoon the seasoned beef mixture into each warmed taco shell. Top with shredded lettuce, diced tomatoes, cheese, sour cream, avocado slices, and fresh cilantro as desired. Serve immediately with lime wedges on the side.