How to Make It
Using a citrus reamer, juice the limes; reserve the peels. In a large resealable plastic bag, mix the lime juice with the chili powder, vegetable oil and 2 teaspoons of salt. Add the crushed rosemary, reserved lime peels and skirt steak. Seal the bag and turn to coat the meat. Let marinate at room temperature for at least 20 minutes and up to 1 hour or refrigerate for up to 4 hours.
Light a grill or preheat a grill pan and brush liberally with vegetable oil. Pat the steak dry and generously season with salt and pepper. Grill the steak over high heat, turning once, until medium-rare, 7 to 8 minutes. Transfer the steak to a work surface and let rest for 5 minutes. Thinly slice the steak diagonally across the grain.
Transfer the steak to a serving platter and serve with the warmed tortillas, chopped onion, sliced radishes, mashed avocado and hot sauce.