Combine the butter, garlic, lime zest, lime juice, and a salt to taste. Set aside. Combine the paprika, cumin, and chipotle powder in a small bowl. Sprinkle the steaks with plenty of kosher salt, then evenly sprinkle the spice mixture over them and rub into the meat.
Oil the grates of the grill (or grill pan) and preheat over high heat until smoking. Reduce heat to medium high and add steaks. Cook without moving until well-charred, about 4 minutes. Flip steaks and continue to cook until center of steaks register 125°F on an instant-read thermometer for medium-rare, 135°F for medium, or 145°F for well done. Transfer to a platter and allow to rest for at least 5 minutes, adding the lime butter after a few minutes to melt from the residual heat.
Slice the steaks and serve immediately.