Trim hangar steak of any visible fat.
In a bowl, add red onion, garlic, tequila, lime juice, Dijon mustard, raw honey, ground cumin, salt and pepper. Whisk to combine. Check seasoning and adjust, if needed.
Using a large gallon size storage bag, place the steak in the bag. Pour the marinade over the steak and seal the bag. Squeeze the bag to ensure marinade coats the steak!
Marinate in the fridge for at least 3 hours or over night.
Heat the grill to 400 degrees, high heat. Remove steak from the marinade, discard marinade. Place steak on the grill. Turn the grill heat down to medium. Grill the steak for about 3 minutes. Flip steak and grill another 4 minutes.
Remove steak from grill. Let rest about 10 minutes. Cut meat against the grain and serve.