In a bowl, combine canola oil, white vinegar, lime juice, garlic powder, sliced jalapeño, chopped cilantro, cumin, and salt. Mix well.
Place the flank steak in a shallow dish or resealable plastic bag. Pour the marinade over the steak, ensuring it's evenly coated. Marinate in the refrigerator for at least 30 minutes or up to 4 hours for maximum flavor.
Preheat the Ninja Foodi Grill to the high grill setting for 10 minutes.
Once preheated, place the marinated flank steak on the grill grate. Grill for 6-8 minutes per side, or until desired doneness is reached, flipping halfway through.
Remove the cooked flank steak from the grill and let it rest for a few minutes. This allows the juices to redistribute, ensuring a juicy steak. Slice the steak thinly against the grain for optimal tenderness.
Serve the grilled flank steak slices hot, garnished with additional cilantro if desired. Enjoy the flavorful and tender steak straight from the Ninja Foodi Grill!