Season the flank steak evenly with chili powder, cumin, sea salt, and black pepper.
Heat the olive oil in a large cast-iron skillet over medium-high heat until shimmering.
Place the steak in the skillet and sear for 4 minutes per side for medium-rare, then transfer to a board to rest.
In the same skillet, sauté the sliced bell peppers and red onion until they are tender and slightly charred.
Prepare the cauliflower rice by lightly sautéing in a separate pan or steaming until tender.
Slice the rested steak against the grain into thin strips.
Divide the cauliflower rice into bowls and top with the steak, peppers, onions, avocado, and fresh cilantro.
Drizzle with lime juice before serving.