Make the marinade: In a large bowl, whisk lime juice, oil, garlic, vinegar, soy sauce or coconut aminos, cumin, chili powder, smoked paprika, oregano, salt, and pepper.
Marinate the steak: Pat the steak dry. Add it to the bowl or a zip-top bag, coat well, and marinate in the fridge for at least 1 hour, up to 8 hours.
Flip once halfway if possible.
Prep the veggies: Slice bell peppers and onion. Toss with a drizzle of oil and a pinch of salt. Shred the cabbage and set aside.
Make the avocado crema: Blend or mash avocado, sour cream, lime juice, and olive oil until smooth.
Season with salt and pepper. Thin with a splash of water if needed.
Cook the veggies: Heat a large skillet or grill pan over medium-high. Sear peppers and onions until slightly charred and tender, 5–7 minutes.
Remove and keep warm.
Cook the steak: Heat the grill or skillet to high. Remove steak from marinade and pat dry for better browning. Cook 3–5 minutes per side for medium-rare, depending on thickness.
Rest and slice: Transfer steak to a cutting board, tent loosely with foil, and rest 5–10 minutes.
Slice thinly against the grain for tenderness.
Assemble the plate: Add a bed of shredded cabbage, top with sliced steak, peppers, and onion. Spoon avocado crema over the top. Add fresh cilantro, avocado slices, and lime wedges.
Finish and serve: Taste and add a final pinch of salt, a squeeze of lime, and a shake of chili flakes if you like heat.