Slice the flank steak into very thin strips against the grain.
In a small bowl, whisk together the chili powder, cumin, garlic powder, sea salt, black pepper, and lime juice.
Toss the steak strips in the spice mixture until evenly coated.
Heat half of the olive oil in a non-stick skillet over medium-high heat and sauté the sliced peppers and onions until tender-crisp, about 4 minutes, then remove from the pan.
Add the remaining oil to the same skillet and sear the steak strips for 2-3 minutes until browned and cooked through.
Wipe the skillet clean and place the corn tortillas in the pan over medium heat.
Distribute the shredded cheddar, sautéed vegetables, and steak onto one half of each tortilla.
Fold the tortillas in half and cook for 1-2 minutes per side until the cheese is melted and the tortillas are golden and crispy.