Pat the flank steak dry with paper towels and season both sides evenly with the ground cumin, garlic powder, sea salt, and black pepper.
Heat the olive oil in a cast-iron skillet over medium-high heat until the oil is shimmering and very hot.
Place the steak in the skillet and sear for 4 to 5 minutes per side for medium-rare doneness, then transfer to a cutting board to rest for at least 5 minutes.
In the same skillet, add the sliced bell peppers and red onion, sautéing for 3 to 4 minutes until they are tender and slightly charred from the steak drippings.
While the vegetables cook, lightly steam the riced cauliflower and toss it together with the cooked brown rice and lime juice in a small bowl.
Slice the rested steak against the grain into thin strips to ensure the meat remains tender and easy to eat.
Assemble the bowl by placing the rice and cauliflower blend at the bottom, then topping with the sliced carne asada, sautéed peppers, and onions.
Finish the bowl with fresh avocado slices and a garnish of chopped cilantro before serving.