In a small bowl, add the garlic, chile powder, salt, brown sugar and cumin.
Rub the spice mixture over the entire skirt steak and let sit for 25 to 30 minutes in a dish or a re-sealable bag.
For the glaze:
Meanwhile, whisk the pomegranate glaze ingredients together in a small saucepan. Bring to a boil over medium heat and simmer until thickened, about 1 minute. Remove from the heat and set aside.
For the steak and vegetables:
Preheat a grill pan over high heat. Place the steak, onion and peppers on grill, if it all fits. If not, cook the steak first and then as the steak rests char up the vegetables. Cook the steak for 3 to 4 minutes per side for medium-rare. Let rest for 5 minutes before slicing against the grain. You want the vegetables to get softened and charred, so they can stay on the grill as the steak rests, about 10 minutes total.
Serve the sliced steak, onions and peppers on the side of warmed tortillas, fresh salsa, sliced avocado, cheese and the pomegranate glaze.