Make the Fajita Marinade

Place the vegetable oil, lime zest and juice, garlic cloves, peeled yellow onion, chipotle peppers, cumin, chili powder, oregano, salt and pepper into a blender or food processor. Blend the marinade up until smooth.

Pour the marinade over the flank steak in a mixing bowl or in a zip top plastic bag. Use tongs in the bowl to coat the entire piece of beef and marinate for at least one hour up to overnight.

Make the Fajita Veggies

In a cast iron skillet over medium-high heat pour in oil and once shimmering hot, put the thin strips of bell peppers and onions in one single layer in the skillet.

Cook the vegetables without moving for about 2 minutes to gain some char, then sprinkle in the salt and pepper and then toss to get color on the other side. Cook the veg until they are slightly softened, but still have a little crunch and bright color.

Take the fajita veggies out of the pan and set aside on a plate.

Cook the Marinated Fajita Meat

About 30 minutes before cooking, take the flank steak out to rest to room temperature.

Use the same skillet as earlier over medium-high heat to give the steak a nice sear. We want some char and a nice crust, it'll take around 3-4 minutes on each side.

Cook the flank steak for about 6 minutes on each side for medium rare. A meat thermometer should read about 128º F to 130º F for med-rare.

After cooking, let the steak rest for about 10 minutes on a cutting board. Slice against the grain and serve with the veggies, warmed corn or flour tortillas, and your choice of toppings.