Season the flank steak evenly with chipotle powder, garlic powder, sea salt, and black pepper.
Heat the olive oil in a cast-iron skillet over medium-high heat until shimmering.
Sear the steak for 4 to 5 minutes per side for medium-rare, then transfer to a cutting board to rest for 5 minutes.
In the same skillet, sauté the sliced bell peppers and red onions for 3 to 4 minutes until they are tender yet slightly charred.
Steam the cauliflower rice in a separate pan or microwave until tender, then stir in the lime juice and chopped cilantro.
Slice the rested steak against the grain into thin strips.
Assemble the bowls by layering the cilantro-lime cauliflower rice, black beans, sautéed vegetables, and sliced steak.
Top each bowl with the fresh avocado slices before serving.