In a bowl, toss the sliced flank steak with chili powder, cumin, salt, and black pepper until evenly coated.
Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Add the steak and cook for 3 to 4 minutes until browned but still slightly pink inside. Remove the steak to a plate.
Add the remaining tablespoon of olive oil to the same skillet. Place the sliced bell peppers and onion in the pan and cook for 5 minutes, stirring often, until they begin to soften.
Stir in the minced garlic and cook for 1 minute more until fragrant.
Return the steak to the skillet along with any juices from the plate. Pour the lime juice over everything and stir to combine. Cook for another minute until heated through.
Warm the flour tortillas in a dry skillet or directly over a low flame for 20 to 30 seconds per side.
Serve the beef and vegetable mixture with the warm tortillas so everyone can build their own fajitas.