2clovesgarlicminced, or pressed with a garlic press
Combine 1/2 cup of the sugar with the wine and bring to a boil, stirring to dissolve the sugar. Add the red onion, cover and cook over medium high heat, stirring occasionally, until softened, about 5 minutes. Drain the onion slices and discard the liquid. Return the onion to the pan. Add the remaining 1/2 cup of sugar and the red wine vinegar and cook over moderate heat, stirring occasionally, until syrupy, about 6 minutes longer.
Meanwhile, light your grill, or broiler or heat skillet In a small bowl, combine the olive oil with the minced garlic, cayenne and cumin. Rub the mixture over the steak and season with salt and pepper. Cook steak until desired doneness. I happen to like medium rare, so about 5 minutes per side. Transfer the steak to a platter and tent for about 5 minutes. Transfer the steaks to plates and top with the red onion marmalade.
If you don't have a skillet large enough for a flank steak, cut the steak crosswise into 4 pieces. Always cut the steak against the grain to serve.