Stir together pineapple juice, cilantro, garlic, cumin, chili powder, paprika, oregano and red pepper in bowl or cup. Reserve 1-1/2 cups for marinade. Set aside remaining sauce.
Step 2
Pour 1-1/2 cups marinade into shallow, non-metallic dish. Add steak, turn to coat; cover and marinate one hour or overnight in refrigerator.
Step 3
Remove steak. Discard marinade. Broil or grill steak and onions 5 inches from heat source for 5 minutes on each side or until done.
Step 4
Combine reserved sauce and cornstarch, in small saucepan. Cook, heat to boiling and sauce slightly thickens.
Step 5
Slice steak into thin strips. Top tortillas with fajita sauce, steak, grilled onions and favorite toppings. Roll tortillas up and serve.
