In a small bowl, combine fine sea salt, black pepper, chili powder, smoked paprika, garlic powder, dried oregano, and red pepper flakes to create the spice mix
2
Slice bell peppers and onion into thin strips, and sirloin steak into thin slices.
3
Heat 2 tablespoons of olive oil in a large, deep skillet over medium-high heat for about 2 minutes.
4
Add the bell pepper and onion strips, and half of the spice mix to the skillet. Cook, stirring often, until just tender, about 5 minutes. Transfer the vegetables to a plate.
5
Add the sirloin steak slices and the remaining spice mix to the skillet. Stir-fry until no longer raw, 3-4 minutes.
6
Return the vegetables to the skillet and stir everything together until heated through, for an additional 1-2 minutes.
7
Optional: If there are too many liquids in the skillet and you want to thicken them, reduce the heat to medium and stir in a cornstarch slurry (1 tablespoon of cornstarch mixed with 1 1/2 tablespoons of cold water). Keep cooking until the liquids thicken, about 1 more minute.