Mix chili powder, cumin, chipotle powder, pepper, and cayenne for rub together in a small bowl.
Place steaks on a large plate. Sprinkle kosher salt generously on both sides, then sprinkle rub over the salt.
Twist 3 pieces of foil into 1/2-inch diameter rolls and place them under the steaks to act as a rack and lift the steaks up from the plate. Pop steaks into the fridge and leave uncovered to dry-brine for 3 to 12 hours.
Meanwhile, place garlic and salt for garlic-lime butter in a mortar. Grind to a paste with a pestle. Add butter and lime zest and stir with a small spoon to combine. Set aside.
Preheat a charcoal grill for high heat. Remove steaks from the refrigerator and brush with vegetable oil on both sides.
Place steaks on the preheated grill and cook until firm and reddish-pink and juicy in the center and meat gently springs back to the touch, about 4 to 5 minutes per side. An instant-read thermometer inserted into the center should read 130 degrees F (54 degrees C) for medium-rare.
Remove from the grill and top with garlic-lime butter.