1. Prepare the beef: In a shallow glass or ceramic dish, combine the vinegar, oil, garlic, orange zest and sugar. Rub the mixture over both sides of the steaks and let marinate at room temperature for at least 15 minutes or for up to 2 hours.
2. Prepare the salad: Roast the poblanos directly over a gas flame or under the broiler, turning, until lightly charred all over; be careful not to burn off too much of their thin skins. Put the chiles in a small bowl, cover with plastic wrap and let steam for 5 minutes. Working over the bowl, peel off all the charred skins and remove the stems and seeds. Strain any accumulated poblano juices into a clean small bowl. Cut the chiles into thin 2-inch strips.
3. In a large bowl, combine the chiles with the garlic, orange juice, oil, vinegar, sugar, orange zest, cumin and 1/2 teaspoon each of salt and pepper. Stir in any reserved poblano juices and set aside for 15 minutes.
4. Light a grill or preheat the broiler. Peel the oranges with a sharp knife, taking care to remove all the bitter white pith. Cut in between the membranes to release the orange sections.
5. Season the meat with salt and pepper. Grill or broil the steaks for about 3 minutes per side, or until nicely browned, crusty and medium- rare. Let the steaks rest for 5 minutes.
6. Remove the garlic from the dressing in the bowl. Add the parsley and onion and toss well. Mound the salad on 4 large plates. Cut the steaks into thin slices and arrange alongside. Garnish with the orange sections and serve.
Wine Recommendation: Pick a red with enough brisk acidity to cope with the raw citrus and sharp parsley. One option is an Italian Barbera, perhaps the 1994 Michele Chiarlo Barbera d'Asti or the 1993 Bruno Giacosa Barbera d'Alba.