In a small mixing bowl, combine chili powder, cumin, paprika, garlic powder, salt, and black pepper.
Toss the steak strips with half of the spice mixture until evenly coated.
Heat 1 tablespoon of olive oil in a large cast-iron skillet over medium-high heat.
Add the steak strips in a single layer and sear for 2 to 3 minutes per side until browned; transfer steak to a plate and set aside.
Add the remaining 1 tablespoon of olive oil to the same skillet.
Sauté the bell peppers and onions for 5 to 6 minutes until the vegetables are tender-crisp and slightly charred.
In a separate pan over medium heat, sauté the riced cauliflower for 4 minutes until tender, seasoning with remaining spice mixture.
Divide the cauliflower rice evenly among four serving bowls.
Top each bowl with the sautéed steak and fajita vegetables.
Garnish with fresh lime juice, chopped cilantro, and avocado slices before serving.