In a large bowl, whisk together lime juice, olive oil, minced garlic, cumin, chili powder, salt, pepper, and chopped cilantro.
Add the skirt steak to the marinade, turning to coat all sides. Let marinate at room temperature for 15 minutes, or refrigerate for up to 24 hours for deeper flavor.
Cook the Carne Asada:
Preheat grill to high heat, or heat a cast-iron skillet over high heat until smoking.
Remove steak from marinade and pat lightly with paper towels (don't remove all the marinade).
Grill or sear the steak for 3-4 minutes per side for medium-rare, or until it reaches your desired doneness. Internal temperature should be 125°F for medium-rare, 135°F for medium.
Transfer steak to a cutting board and let rest for 5 minutes.
Slice the steak against the grain into thin strips, about 1/4-inch thick.
Assemble and Serve:
Warm tortillas in a dry skillet for 30 seconds per side, or wrap in damp paper towels and microwave for 30 seconds.
Fill each tortilla with sliced carne asada, diced onions, and chopped cilantro.
Serve immediately with lime wedges, salsa, and crumbled queso fresco on the side.
Notes
Storage tip: Leftover carne asada keeps in the refrigerator for up to 4 days. Reheat gently in a skillet with a splash of broth. For meal prep, store sliced meat and toppings separately, then assemble tacos as needed throughout the week.