Make Carne Asada tonight: marinate flank steak for 4 hours, then grill to a juicy, charred finish.
Toss the garlic cloves, halved and seeded jalapeño, a generous handful of cilantro (leaves and tender stems), the lime and orange juices, extra-virgin olive oil, chili powder, ground cumin, and kosher salt into a blender or small food processor. Pulse until the mixture becomes a coarse, emerald-green emulsion—bright, slightly chunky from little cilantro leaf flecks and specks of chili, glossy from the oil, with a thin citrus sheen. Scrape the sides, taste briefly for balance, and transfer the fragrant, herb-forward marinade into a glass jar or the blender pitcher for the next step.
Place the flank or skirt steak in a clear, heavy-duty zip-top bag or an airtight container and pour the blended marinade over the meat so it adheres in an even, herb-speckled coat. Remove excess air, seal, turn the bag to thoroughly coat every surface, and lay it flat so the marinade makes full contact. Refrigerate for at least four hours and up to twelve—enough time for the citrus and salts to tenderize and for the cilantro, garlic, and chiles to infuse deep savory aromatics into the muscle fibers.

Forty-five minutes before cooking, remove the marinated steak from the refrigerator and let it sit, sealed or covered, on the countertop to come up to room temperature. This short warm-up evens the internal temperature so the steak sears predictably, keeping the exterior from overcooking while the interior reaches the perfect warm-pink doneness.
Preheat half of a gas or charcoal grill to high so you get a fierce sear while leaving a cooler zone nearby; clean the grates so the meat releases cleanly. Sear the steak over the hot zone, turning every few minutes, until the center reads about 110°F on an instant-read thermometer—this usually totals roughly 6 to 10 minutes depending on thickness. The exterior should develop a deeply caramelized, slightly charred crust with visible grill lines while the interior remains rosy and tender.
Transfer the grilled steak to a wooden cutting board and let it rest for five minutes so juices redistribute; you should see a slight pooling of glossy juices beneath the meat. Using a sharp knife, slice thinly across the grain into narrow, ribbon-like strips that showcase a contrast between the crusty, bronzed exterior and the warm pink interior. Arrange the slices overlapping on a shallow, rustic platter, scatter a few cilantro leaves, tuck halved limes nearby, and serve alongside bowls of rice or tortillas for a ready-to-enjoy Carne Asada.
