Slice the chicken breast and sirloin steak into thin, uniform strips against the grain to ensure tenderness.
In a small bowl, whisk together the chili powder, cumin, garlic powder, sea salt, and black pepper.
Toss the meat strips in half of the spice mixture until every piece is evenly coated.
Heat the avocado oil in a large cast-iron skillet over medium-high heat until it begins to shimmer.
Add the steak and chicken to the skillet in a single layer, searing for 3-4 minutes until browned and cooked through, then remove and set aside.
Add the sliced bell peppers and onions to the same skillet, sprinkling with the remaining spice blend.
Sauté the vegetables for 5 minutes until they are tender-crisp with slightly charred edges.
Return the meat to the skillet, toss with lime juice to deglaze the pan, and garnish with fresh cilantro before serving.