Wash and pat the flank steak dry. Pierce steak all over with a fork to allow marinade to penetrate meat.
Mix together all the marinade ingredients. Place flank steak in a Ziploc bag, pour marinade over steak, seal bag and refrigerate for at least four hours, or over night.
Heat griddle over medium high heat. Make sure to have the oven vent on high as things can get smoky.
I have a built-in cast iron griddle on my stove top, but you could use a griddle pan, or a cast iron skillet. If using a skillet, you will probably need to work in batches, or you could use two skillets.
While the griddle is preheating chop your vegetables. To save time, I continue to chop as the vegetables are cooking.
Add olive oil to the hot pan.
I usually start by adding the peppers to the pan first, because they take a bit longer to cook. When the peppers begin to char in places, (about 4 minutes), I add the onions. Toss with tongs to break the onion slices up. When the onions soften, (about 4 minutes), add the scallions and cook for about 3 minutes.
Sprinkle the chili powder, adobo, salt and pepper over the vegetable mixture and stir.
Add the garlic and quickly stir it into the vegetables. By the time you get the garlic incorporated, it’s time to get the veggies off the griddle.
Transfer the vegetables to a large bowl. Stir in the chopped cilantro, and add lime juice from half of the lime. Note: I just hand squeeze the lime, which yields about 1 Tbs of juice. Cover bowl to keep warm.
Raise the heat on the griddle to high, (or you could cook the steak on a an outside grill).
Remove steak from marinade, and pat dry. It does not need to be bone dry, but if it is too wet, it will not sear.
Cook steak to the temperature you want, turning once. I had a thin steak, which took 3 minutes per side to reach medium-rare.
Let steak rest for at least 5 minutes.
Meanwhile, gather your favorite condiments; I like pico de gallo salsa, guacamole, and sour cream.
Cut the steak on the bias, in thin slices against the grain.
You can assemble fajitas onto a lettuce leaf wrap or over a green salad. I like to eat mine right on a plate. I dip my steak in the salsa or guac, and grab some veggies with each bite.
You could also serve these with paleo tortillas. I have not found a nut-free paleo tortilla recipe that I like yet, (I’m allergic to nuts).
My kids prefer their fajitas with flour tortillas, of course.