Place the steak into a shallow pan or casserole dish.
Add the olive oil, Negra Modelo, zest, juice and soy sauce.
Using tongs flip the meat over a few times making sure the marinade coats all of it.
Let rest for 30 minutes in the fridge, or overnight.
Slice the peppers into thin strips and place in a large bowl.
Slice the onion in half and then into thin slices, add to the peppers.
Heat your grill to maximum.
Place the steak carefully onto the heat and sear for about 3 minutes.
Flip the steak over and repeat on the other side for another 2-3 minutes or longer if you prefer the meat well done.
Transfer the steak to a plate and let to rest while you cook the vegetables.
Heat a large pan over a high heat.
Add the bowl of peppers and onion followed by the leftover marinade from the steak.
Cook quickly for about 5 minutes until the vegetables start to soften.
Turn off the heat and slice the skirt steak diagonally into thin strips.
Place on a platter with the cooked peppers and onion. Garnish with fresh chopped cilantro.
Serve with warm flour tortillas, salsa and guacamole on the side if desired.
