Preheat your cast iron skillet over medium-high heat until it’s just starting to smoke, creating a hot surface perfect for searing.
Add a tablespoon of oil to the skillet, swirling to coat the bottom. Once shimmering, add the sliced peppers and onions. Stir quickly and cook, stirring frequently, until the vegetables are charred around the edges and just tender, about 5-7 minutes. You’ll hear them sizzle and see them blister and soften.
While the vegetables cook, pat the thinly sliced steak dry with paper towels to ensure a good sear. In a small bowl, mix the cumin, smoked paprika, chili powder, and a pinch of salt. Toss the steak slices with the spice mixture and lime juice, letting them marinate briefly if time allows.
Push the cooked peppers and onions to one side of the skillet. Add a little more oil if needed, then carefully place the steak slices in the empty space. Sear the steak for 1-2 minutes per side, watching for a golden brown crust to form. The steak should turn juicy and slightly caramelized on the edges.
Once the steak is cooked through and browned, toss it together with the peppers and onions in the skillet, allowing the flavors to meld for another minute or so. The mixture should be fragrant, with a smoky aroma filling the air.
Meanwhile, warm the tortillas in a dry skillet or microwave until soft and pliable, about 30 seconds. Keep them covered to prevent drying out.
Squeeze fresh lime juice over the cooked steak and vegetables for a bright, citrusy finish. Serve the sizzling mixture on warm tortillas, allowing everyone to assemble their own fajitas.
