In a blender or small food processor, pulse the garlic, jalapeno, cilantro, lime juice, orange juice, olive oil, chili powder, cumin, and salt.
Place the steak in a zip-top bag or an airtight container and cover with the marinade. Seal and turn to coat. Refrigerate for at least 4 hours and up to 12 hours (do not marinate longer or the meat will start to break down).
Forty-five minutes prior to cooking, remove the steak from the refrigerator to allow to come to room temperature.
Preheat half of a gas or charcoal grill to high heat (preheating only half will keep the grill from getting *as* hot). Clean the grates if necessary. Place the steak over the heat, cover, and cook until the center reaches 110°F on an instant-read thermometer, turning the steak every few minutes, about 3-5 minutes per side total (that’s 6 to 10 minutes total for the whole steak; DO NOT overcook!). Transfer the steak to a cutting board and rest for 5 minutes. Cut across the grain into very thin strips.
Notes
TO STORE: Leftover carne asada can be stored in an airtight container in the refrigerator for 3 to 4 days.
TO REHEAT: Reheat carne asada in a skillet or on the grill until warmed through. Alternatively, you can microwave it, but this isn’t ideal.
TO FREEZE: Once the meat has been cooked, you can freeze it in an airtight container or freezer-safe bag for up to 3 months. Thaw in the refrigerator before reheating.