Marinate steaks,covered and chilled, at least 30 minutes and up to 1 day.
Season steaks generously with coarse salt and grill on a rack set 5 to 6 inches over glowing coals 2 to 3 minutes on each side for medium-rare.
(Alternatively, steaks may be broiled on rack of a broiler pan under a preheated broiler 3 inches from heat about 4 minutes on each side.) Transfer steaks to a cutting board and drizzle with lime juice.
Let steaks stand, uncovered, 5 to 10 minutes and with a sharp knife cut diagonally across grain into thin slices.
Garnish with grilled onions, serve with tortillas, refried beans and rice.