Look in the refrigerated precut produce section for a blend of sliced multicolored peppers. If starting from whole peppers, use about 2 medium peppers of each color (this step can also be done ahead).
How to Make It
Preheat broiler with oven rack in the top position. Place a rimmed baking sheet in oven (leave pan in oven as it preheats).
Combine oil, cumin, 1/2 teaspoon salt, chile powder, and black pepper in a bowl, stirring with a whisk. Place steak in a bowl. Place bell peppers and onion in a bowl. Add half of oil mixture to steak; toss. Add remaining half of oil mixture to pepper mixture; toss.
Carefully remove baking sheet from oven. Coat pan with cooking spray. Add pepper mixture to pan; broil 10 minutes or until almost tender. Remove pan from oven. Move pepper mixture to sides of pan; arrange steak in center of pan. Broil 3 minutes or until steak reaches desired degree of doneness. Sprinkle cilantro and lime wedges over pan.
Combine remaining 1/4 teaspoon salt, sour cream, lime juice, and ground red pepper in a small bowl, stirring with a whisk. Heat tortillas according to package directions. Serve sour cream mixture and tortillas with steak and pepper mixture.
Easy Peasy