Beef with Chimichurri Sauce and Onion/Pepper Salad

Sue and I were trying to remember when chimichurri sauce -- a savory, spicy, parsley-based meat sauce of Argentinean origin -- made its first real appearance on the popular culinary scene. It was the same time as Argentinean beef restaurants became the "in" thing in New York City, but when was that? Five years ago? More? At any rate, red meat's comeback has been (temporarily, perhaps) delayed by mad cow disease and other health issues; but this chimichurri sauce is something we don't want to forget.
Ingredient

6 to 8 soft flatbreads
(see recipe:Soft Wrap Bread)

Beef and Marinade
3 cloves garlic, peeled
1 teaspoon salt
1 teaspoon ground black pepper
1 tablespoon olive oil
a dash or two of hot pepper sauce
1 tablespoon red wine vinegar
1 to 1 1/2 pounds flank steak

The Sauce
3 cloves garlic, peeled 1 1/2 cups chopped parsley (1 large bunch, about 5 ounces)
2 tablespoons (1 ounce) red wine vinegar
1 teaspoon salt
1 teaspoon ground black pepper
4 tablespoons (1 3/4 ounces) olive oil
1 teaspoon hot pepper flakes or half of a small hot pepper (such as jalapeño), seeded

The Salad
2 medium red or sweet onions (10 to 12 ounces), peeled
2 medium red peppers (10 to 12 ounces)
1/4 to 1/2 teaspoon salt
2 cloves garlic, peeled and crushed
1 tablespoon red wine vinegar
1 tablespoon olive oil
Beef and Marinade

Crush the garlic cloves, then mix them with the remaining marinade ingredients. Rub both sides of the meat with the marinade (which will be more like a paste), then place it in a plastic bag or shallow bowl with a cover. Keep it refrigerated until ready to grill, up to 24 hours.

The Sauce

Crush or mince the garlic. Clean the parsley, removing the tough stem ends. Chop the parsley medium-fine, then mix it with the remaining ingredients. A food processor works well here; place the parsley leaves (and small stems) in the bowl of your food processor, add the remaining ingredients EXCEPT the oil, and pulse a few times, till the mixture is coarsely combined (don't let it get smooth). Stir in the oil, and keep the sauce refrigerated until you're ready to use it; it can be prepared 1 to 2 days ahead of time.

The Salad

Slice the onion and pepper thinly, and stir in the remaining ingredients. Let the salad sit for several hours (or overnight) in the refrigerator; it'll soften nicely, and the flavors will meld.

Serving: Grill the steak to the degree of doneness you like. Let it rest for 5 minutes off the grill, to help it retain its juices. Slice it thinly across the grain. Spread some chimichurri sauce on the warmed bread, add thin slices of meat, then top with the peppers and onions. Roll up, if desired. Yield: 8 sandwiches.