Place Marinade ingredients in a large bowl and whisk to combine. Add chicken or beef to a zippered bag. Toss well to coat. Marinade for several hours. When ready to cook, cut peppers and onion in strips. Heat 2 tablespoons of olive oil in a heavy skillet over high heat. Add vegetables to skillet and cook until softened and charred. Sprinkle with salt and pepper to taste. Set aside. Cook chicken or beef in the same skillet until browned. Slice chicken or beef into strips. Heat tortillas in dry skillet. Assemble fajitas with chicken or beef, peppers and onions. Finish with toppings.