Mix the cumin, chili powder, brown sugar, garlic powder, cornstarch and salt in medium bowl. Add the chicken strips; toss until coated. Heat the oil in large nonstick skillet over medium-high heat. Add the chicken to the skillet. Cook and stir for 5 to 7 minutes or until no longer pink in the center. Add the onion and pepper mix; cook for an additional 3 to 5 minutes or until thoroughly heated, stirring frequently. Meanwhile, warm the flour tortillas as directed on package. For each, spoon 1/4 cup chicken mixture on one half of the tortilla. Top a dollop of sour cream. Fold over to serve.