"Upscale steak tacos usually get their rich, beefy flavor from the grill, but cooking outdoors isn’t always possible. We wanted an indoor cooking method that would always yield steak taco meat as tender, juicy, and rich-tasting as the grilled method. We didn’t want to wrap a pricey cut of beef in a taco, so we explored inexpensive cuts and chose flank steak for its good flavor and ready availability; when sliced against the grain, it can be just as tender as pricier cuts. To add flavor, we poked holes in the meat with a fork and rubbed it with a paste of oil, cilantro, jalapeño, garlic, and scallions; salt helped draw all the flavors into the steak and ensured juiciness. Pan-searing, with a sprinkling of sugar to enhance browning, gave us a crust that mimicked the char of the grill. To maximize this effect, we cut the steak into four long pieces, which gave us more sides to brown and turn crispy. For additional flavor, we tossed the cooked steak with some marinade that we had reserved and garnished the tacos simply with onion, cilantro, and lime wedges. In Mexico, steak tacos are often served with curtido, a relish of pickled vegetables; we devised a quick recipe for pickled onions to accompany our good-as-grilled steak tacos...."