Heat 2 Tablespoons olive oil in large skillet over medium heat. Add 12 ounce steak and remaining red onions, season with salt and pepper to taste, and cook until steak is mostly cooked through. Add 2 cloves garlic and sauté another 30 seconds.
Add ½ cup barbecue sauce, 2 teaspoons chili powder, ½ teaspoon paprika, ½ teaspoon ginger, ¼ teaspoon cumin, 1 teaspoon chipotle sauce, 1 cup pineapple and simmer for 3-5 minutes, or until steak is cooked through and barbecue sauce is warmed. Remove from heat and stir in ½ cup cheese. Taste and adjust seasonings and heat as desired.
Preheat oven to 350 degrees and line a baking tray with foil and place a baking rack on top of it.
Divide flauta filling evenly between tortillas and roll as tightly as possible. If you like, save some of the filling to be served on top of the flautas. Optionally, cut off about ⅓ of the tortillas before rolling if you want less tortilla.
Brush both sides of each flauta lightly with olive oil, and place on rack, seam side down.
Cook flautas for 10 minutes, then turn oven to broil. Broil flautas until golden brown, 2-3 minutes, watching closely so they don’t burn. Flip flautas over and broil the other side until crispy.
Top individual servings of flautas with more filling or barbecue sauce and pineapple salsa.