Combine the orange juice, grapefruit juice, garic, onion, and cilantro in a large ziplock bag. Cut the steak in manageable pieces and add to the bag.

Place the bag with steak and marinade into the fridge for 3 hours to overnight.

Remove the steak from the marinade and pat dry with a paper towel.

Fire up your grill or place a cast iron skillet on the stove over high heat. Cook the steaks on each side until you get a good sear. Do not cook skirt steak past medium or it will be tough.

Let yout steak rest for 5 minutes. While the steak rests lightly grill or broil your torillias, until they just start to get some color.

Cut your steak into 3 inch long pieces. Then slice thinly against the grain.

Construct your tacos with two tortillas each so they don't fall apart. Add your meat and top with the pico and chimichuri. Serve immediately.