Combine marinade ingredients in a shallow dish. Turn flank steak in marinade and let stand 15 minutes. The meat can be placed in marinade in the morning and allowed to marinate until suppertime if you enjoy very strong, spicy flavors. The short marinade will result in a milder tasting meat which is more palatable to many not-too-hot taste buds.
Follow directions on packaged rice and get it simmering, it will take 18 to 20 minutes.
Heat a grill pan to high heat and sear the flank steak 4 minutes on each side. Reduce heat and cook meat 6 to 8 minutes longer, turning occasionally.
Heat a medium nonstick skillet over high heat. Blister tortillas 30 seconds on each side and stack them on a plate. Loosely wrap tortillas with foil and place them on the dinner table. Add oil to hot pan and sear sliced peppers and onions for fajitas. Season peppers and onions with salt and pepper. Char edges and stir-fry the peppers and onions until just tender, 2 or 3 minutes. Transfer to a platter and cover with loose foil to keep hot. Add another tablespoon oil, garlic, jalapeno and chopped onion; saute for 2 minutes. Add black beans and spices to the pan and heat through for another 1 to 2 minutes. Transfer beans to a serving dish. Top beans with cilantro and scallions.
Remove meat from grill pan and let it rest 5 minutes for juices to distribute. Transfer peppers and onions to grill to get the sizzle effect going. Slice meat very thin on an angle against the grain. Pile meat on top of cooked peppers and onions and take the hot grill to the table, letting rest on trivets or a cool wire rack. Stack meat and veggies in warm tortillas and enjoy with a side of spicy black beans.