2 teaspoons smoked paprika 2 teaspoons dried oregano 1 1/2 teaspoons garlic powder 1 1/2 teaspoons ground cumin 1 teaspoon brown sugar 1/4 teaspoon kosher salt 1/4 teaspoon freshly ground black pepper 1/8 teaspoon ground red pepper 1 (1-pound) flank steak, trimmed Cooking spray 1 small red onion, cut into 1/4-inch slices 1 small red bell pepper, cut into 1/2-inch slices 1 small yellow bell pepper, cut into 1/2-inch slices 8 corn tortillas 1/4 cup chopped cilantro 8 lime wedges (optional)

Combine paprika, oregano, garlic powder, cumin, brown sugar, salt, black pepper, and red pepper in a small bowl. Rub 2 tablespoons spice mixture evenly over steak.
Heat a grill pan over medium-high heat. Coat pan with cooking spray. Add steak to pan; grill 5 minutes on each side or until desired degree of doneness. Place steak on a cutting board; let stand 10 minutes. Cut across the grain into thin slices.
Combine remaining 2 1/2 teaspoons spice mixture, onion, and bell peppers in a bowl; toss to coat. Arrange onions and peppers on pan; grill 5 minutes on each side or until lightly charred. Remove vegetables from pan. Add tortillas to pan; grill 30 seconds on each side or until lightly browned.
Divide steak and bell pepper mixture evenly among tortillas. Top with chopped cilantro. Serve with lime wedges, if desired.