Place the steaks in a nonreactive shallow pan.
Combine 3 tablespoons (45 ml) olive oil, the white wine vinegar, coriander seeds, mustard, garlic, and red pepper. Spoon this mixture over the steaks, turning the pieces to coat both sides. Marinate in the refrigerator for at least 1 hour, turning the meat once or twice during that time.
Preheat the oven to warm (lowest temperature). Heat the remaining 2 tablespoons (30 ml) olive oil in a large sauté pan over medium heat. Add all the peppers and the onion and sprinkle with salt. Sauté, stirring occasionally, for 8 to 10 minutes, or until the vegetables have softened and are beginning to brown.
Spoon the mixture into an ovenproof dish and keep warm in the oven. Turn the heat under the sauté pan to medium-high. Add the steaks and cook for 3 to 5 minutes per side or until cooked to the desired doneness. Place the steaks on top of the peppers (or surround the meat with the peppers) and serve.
SERVING SUGGESTIONS AND VARIATIONS: You can make this dish with skirt steak. Use any kind of peppers you wish; the ones suggested here add color and a range of tastes from hot to sweet. The sweet onions give a good balance to the peppers, but common yellow onions will do, too.
Source: The Modern Kosher Kitchen Cookbook