Prepare the steak: Trim any excess fat from the skirt or flank steak. If the steak is very thick, you can slice it in half horizontally to create thinner, more even pieces for better marinating.
Combine marinade ingredients: In a blender or food processor, combine the lime juice, olive oil, cilantro, garlic, onion, jalapeƱos (if using), cumin, oregano, salt, pepper, and orange juice.
Blend until smooth: Process the mixture until it forms a relatively smooth, vibrant green marinade.
Marinate the meat: Place the steak in a large, resealable plastic bag or a non-reactive dish. Pour the marinade over the steak, ensuring every surface is coated.
Refrigerate: Seal the bag or cover the dish and refrigerate for at least 4 hours, but preferably 8 to 12 hours for the best flavor penetration. Do not marinate for more than 24 hours, as the acid in the lime juice can start to break down the meat too much.
Grill: Remove the steak from the marinade, letting excess drip off. Discard the remaining marinade. Grill over high heat for 3 to 5 minutes per side for medium-rare, depending on the thickness of your steak.
Rest and slice: Let the grilled carne asada rest for 5 to 10 minutes before slicing thinly against the grain.
Notes
For an extra smoky flavor, add 1 teaspoon of smoked paprika to the marinade mixture.
If you prefer a less intense citrus flavor, reduce the lime juice by 1/4 cup and substitute with water.
This marinade works perfectly for flank steak carne asada or skirt steak carne asada.