Slice the flank steak into thin strips against the grain and season evenly with sea salt, black pepper, chili powder, and cumin.
Heat the olive oil in a large cast-iron skillet over medium-high heat until shimmering.
Add the steak strips to the skillet in a single layer and sear for 3-4 minutes until a brown crust forms, then remove from the pan and let rest.
In the same skillet, add the sliced bell peppers and red onion, sautéing for 5 minutes until they are tender yet still slightly crisp.
Steam or lightly sauté the cauliflower rice in a separate pan for 3-4 minutes until softened.
Mash the avocado with a splash of lime juice to create a simple guacamole.
Assemble the bowl by placing the cauliflower rice at the base, followed by the steak and sautéed vegetables.
Top with the guacamole, shredded cheddar cheese, and fresh cilantro, finishing with the remaining lime juice.