In a small, heavy saucepan, combine all the marinade ingredients and bring to a simmer over medium heat. Cook for about 10 minutes, stirring occasionally. Remove from the heat. Set aside and let cool to room temperature.
Lay each steak flat on the counter and tie each one horizontally so that the meat forms a tight, round package. You will need 6 pieces of kitchen twine, each measuring about 18 inches long.
Spread half the marinade over the bottom of a nonreactive casserole or deep baking pan just large enough to hold all 6 steaks snugly but without crowding. Arrange the steaks in the pan and coat with the remaining marinade. Cover and refrigerate for at least 3 hours or up to 5 hours.
Remove the steaks from the marinade and place them on a double thickness of paper towels to dry.
Light a fire in a charcoal grill or preheat a gas grill to medium.
Set the peppers over the hottest part of the grill and cook until they begin to char. Turn with tongs and continue grilling until the peppers are charred on all sides. Stand by the grill during this time, the peppers cook quickly. Using tongs to turn them prevents them from splitting open. Transfer immediately to a container just large enough to hold them. Cover tightly with plastic wrap and let the peppers cool to the touch. Rub the charred skin off the peppers. Remove the seeds and ribs from the peppers. Cut the peppers into strips.
About 15 minutes before grilling, remove the steaks from the refrigerator and let sit at room temperature. Season the steaks with salt and pepper and brush with half the oil. Grill for 7 minutes on 1 side. Turn and grill for 7 minutes longer on the other side. Turn 1 more time and grill for about 2 minutes longer for rare steak. Grill for 1 to 2 minutes longer for medium-rare. Take care when turning the steaks to that the grill marks on the meat are perpendicular to the grate.
Transfer the steaks to a warmer platter and remove the twine.
Place a medium saute pan or skillet on the hottest part of the grill. Put the remaining 1 1/2 tablespoons oil and the sliced onions in the pan and cook, stirring, for about 5 minutes, or until the onions are lightly browned. Add the pepper strips and cook for about 2 minutes, or until heated through.
Serve the steaks on warmed large plates with the grill marks showing. Carefully spoon the pepper and onions over half of each steak so that the grill marks are clearly visible.
Put the cloves in a dry cast iron skillet and cook over low heat for 20 to 30 minutes, or until softened. Turn frequently so that the cloves soften but do not brown. Slide the cloves from the skillet onto a plate to cool to the touch. Squeeze the softened garlic pulp from the individual cloves.