In a large Ziploc bag or shallow dish, combine olive oil, lime juice, orange juice, chili powder, cumin, smoked paprika, dried oregano, minced garlic, minced jalapeño, salt, and black pepper. Add the skirt steak, ensuring it's fully coated. Seal the bag (or cover dish) and refrigerate for at least 30 minutes, or up to 2 hours.

While the steak marinates, prepare the pico de gallo. In a medium bowl, combine diced tomatoes, red onion, cilantro, minced jalapeño, fresh lime juice, and salt. Stir well and set aside.

If making the crema, combine avocado, sour cream (or Greek yogurt), lime juice, 1 tablespoon of water, and a pinch of salt in a blender or food processor. Blend until smooth and creamy, adding more water if needed to reach desired consistency. Set aside.

Preheat a grill to high heat or a heavy cast-iron skillet over high heat until smoking. Remove the steak from the marinade, letting any excess drip off. Discard the remaining marinade.

Place the steak on the hot grill or skillet. Cook for 2-4 minutes per side for medium-rare, or longer for desired doneness. Skirt steak cooks quickly due to its thinness.

Transfer the cooked steak to a cutting board and let it rest for 5-10 minutes. This allows the juices to redistribute, ensuring a tender steak. Slice the steak against the grain into thin strips.

While the steak rests, warm the tortillas. You can do this by placing them directly over a gas flame for 10-20 seconds per side until pliable and lightly charred, or wrap them in damp paper towels and microwave for 30-60 seconds, or heat them in a dry skillet.

Lay out the warm tortillas. Distribute the sliced skirt steak evenly among them. Top generously with pico de gallo and a drizzle of avocado crema (if using). Add any other desired toppings like cotija cheese or pickled red onions.

Serve immediately and enjoy your delicious Skirt Steak Tacos!