In a large ziplock bag, combine orange juice, lime juice, minced garlic, cumin powder, coriander powder, onion powder, chipotle powder, salt, and pepper. Add the beef, seal it tightly, and massage the marinade into the meat. Refrigerate for at least 2 hours, or overnight for more flavor.

Remove the marinated beef from the fridge and let it come to room temperature for about 30 minutes. Pat it dry using paper towels and discard the leftover marinade.

Drizzle about half a tablespoon of oil on each side of the beef, totaling about 1 tablespoon. Heat a BBQ grill or skillet on high heat and cook the beef for about 4-6 minutes per side for medium rare. Transfer to a plate and cover loosely with foil.

Return the skillet to high heat, add another half tablespoon of oil, toss in the sliced onions and season with salt and pepper. Cook until soft and charred. Remove to a serving plate.

In the same skillet, add the remaining half tablespoon of oil, add the sliced bell peppers, season with salt and pepper, and sauté until tender and charred.

Slice the rested beef very thinly against the grain for tenderness.

Warm the tortillas, then fill them with slices of beef, sautéed onions, and bell peppers. Add toppings like avocado, cilantro, sour cream, lime wedges, and fresh tomatoes or Pico de gallo.