In a plastic storage bag or baking dish, whisk together all of the marinade, adding the cilantro at the end.
Set aside 1/4 cup of the marinade.
For the flank steak:
If you wish to cook the flank steak whole, add it to the marinade, cover or seal, and refrigerate for 2-24 hours. Otherwise, slice the meat against the grain very thin and add to the marinade.
If cooking the meat in slices: heat a grill to medium high heat and add the meat to the grill, carefully laying it across the grates so it does not fall through.
Cook for 2 minutes per side or just until grill marks appear and then remove to the serving dish with the peppers, drizzle with the reserved marinade.
If cooking the meat whole: as soon as you place the meat on the grill, turn it down to medium. Cook for 6-7 minutes per side or until desired temperature.
Remove to a cutting board and allow to rest with a piece of foil draped over the top for 5 minutes.
Slice thin and serve with peppers.
For the Peppers and onions:
In a cast iron skillet (we prefer this one from Lodge), over medium heat add the butter and oil.
Add the peppers and onions and the seasoning.
Once the veggies begin cooking, turn the heat to medium low and while stirring occasionally, allow to cook for about 20 minutes or until golden and tender.
Add the meat and serve immediately.
To cook indoors: slice the meat thin and marinate. Right before the peppers and onions are ready for serving, remove them from the cast iron and turn the heat to medium high. Add the meat, cooking on one side for about a minute or two, then stir and repeat until the meat is desired temperature. We usually stick with about 4 minutes total so it's not well done. Turn the heat to low and add the peppers and onions back in, cook for another minute and serve.
Will keep for 3-4 days in the refrigerator.
Steak Fajitas Marinade
Amount Per Serving (1 g)
Calories 337Calories from Fat 171
% Daily Value*
Saturated Fat 6g38%
Polyunsaturated Fat 11g
* Percent Daily Values are based on a 2000 calorie diet.