Preheat oven to 400ºF.
Turn on grill to medium-high heat.
In a blender, add Primo's Garlic Olive Oil, yellow onion, black pepper, and red wine vinegar and blend until smooth. Pour the mixture into a resealable container or bag with the sirloin, seal it, and turn/shake it to coat the meat. Chill for at least 30 minutes.
In a baking dish, add the red onions and Primo's Pineapple White Balsamic Vinegar. Roast in the oven for 20-30 minutes, or until onions are tender and browned on the edges.
While onions are roasting, remove the sirloin from the marinade and shake off any excess. Grill the steak for 6-7 minutes per side, or until your desired degree of doneness. Transfer meat to a cutting board to rest for 5-10 minutes.
Grill the red pepper on each side until it's tender. When it's cool enough to handle, remove the stem and seeds from the roasted pepper, then julienne it.
Slice the steak into thin strips. Place a few strips on each tortilla, then top with balsamic onions and red pepper. Add any additional toppings of your choice. Serve and enjoy!