01 - Preheat your oven to 350°F. Arrange the hard taco shells on a baking sheet and warm them for 5-7 minutes, or according to package directions, until they are crisp.
02 - Heat a large skillet over medium heat. Add the ground beef and cook, breaking it apart with a spatula, until it is thoroughly browned, approximately 5-6 minutes. Drain any accumulated excess fat.
03 - In the same skillet, add the finely diced yellow onion and cook for 2 minutes until softened. Stir in the minced garlic and cook for an additional 30 seconds until fragrant.
04 - Incorporate the tomato paste, chili powder, ground cumin, smoked paprika, dried oregano, salt, and black pepper into the beef mixture. Stir continuously for 1 minute to ensure the beef is evenly coated with the spices.
05 - Pour in the beef broth or water. Reduce the heat to low and allow the mixture to simmer gently for 5-7 minutes, stirring occasionally, until the liquid has mostly evaporated and the filling achieves a saucy, not soupy, consistency. Taste and adjust seasonings as necessary.
06 - To assemble, fill each warm taco shell with a generous spoonful of the seasoned beef mixture. Garnish with shredded iceberg lettuce, diced tomatoes, shredded cheddar cheese, and any other desired toppings such as sour cream, black olives, or jalapeños.
07 - Serve the assembled tacos immediately, accompanied by fresh lime wedges for squeezing.