- Heat a gas grill to medium or light a charcoal fire and let it burn until the coals are covered with a gray ash. Turn off the heat in the middle of the gas grill or bank the coals to the sides for indirect cooking.
- Season the ribs liberally with salt and pepper. Place ribs in a rib rack if you have one and grill indirectly over medium heat (turning ribs once or twice if you are not using a rib rack). When the ribs have cooked for 1 1/4 hours, start basting them every 15 minutes or so with the Frontera BBQ Sauce until the meat is very tender and has shrunk from the ends of the bones, 1 1/2 to 2 hours total. Place the pineapple slices (lightly brushed with oil) over the hottest part of the grill during the last 5 minutes of cooking. Turn the pineapple so both sides are golden.
- Remove the ribs from the grill to a heated platter. Serve with remaining sauce and the grilled pineapple slices. Garnish with sprigs of cilantro.