Chop the red onion finely and set aside. Juice the lime and chop the cilantro, preparing both for toppings.
Heat the cast iron skillet over medium-high heat until hot, about 200°C (390°F). Add a splash of oil, swirling to coat the surface.
Add the ground beef to the hot skillet, breaking it apart with a spatula. Cook for about 8-10 minutes until browned and slightly crispy, stirring occasionally to promote even searing.
Stir in chili powder, cumin, salt, and pepper into the beef, cooking for another minute until fragrant and well coated.
Meanwhile, warm the tortillas in a microwave for 20 seconds or in a dry pan until soft and slightly toasted around the edges. Cover with a towel to keep warm.
Once the beef is cooked and flavorful, remove the skillet from heat. Squeeze fresh lime juice over the meat and stir to combine.
Assemble the tacos by placing a generous spoonful of seasoned beef onto each warm tortilla.
Top each taco with chopped red onion and cilantro for fresh brightness and crunch.
Serve immediately while the tacos are warm, garnished with extra lime wedges if desired.
