1: Heat oven to 475 degrees.
2: Toss bell peppers, onion, garlic, oil, salt, and pepper together on a rimmed baking sheet and spread into an even layer.
3: Roast until vegetables are lightly browned around edges, about 10 minutes.
4: Combine chili powder, brown sugar, salt, and pepper in a bowl.
5: Cut steak lengthwise with grain into 3 equal pieces. Pat steaks dry with paper towels and sprinkle with the spice mixture.
6: Wrap tortillas in aluminum foil and set aside.
7: Remove sheet from the oven, push vegetables to one half of the sheet.
8: Place steaks on the other half of the sheet, leaving space between them.
9: Roast until vegetables are spotty brown and meat registers 135 degrees (for medium), about 8 minutes.
10: Transfer steaks to a cutting board and let rest, uncovered, for 5 minutes.
11: Place the tortilla packet in the oven until warm, about 5 minutes.
12: Transfer vegetables to a serving platter and toss with lime juice.
13: Slice the steaks thin against the grain and transfer to the platter with vegetables.
14: Sprinkle with cilantro and serve steak and vegetables with warm tortillas.
