Instructions (Steak Marinade)

1. Add steak to a large plastic bag or casserole dish.
2. Remove 1/4 cup of the marinade and transfer to a small bowl. Whisk in lime juice and set aside.
3. Pour the remaining marinade over the beef, flip several times to coat. Marinate for 30 minutes, flipping halfway through. The beef can be refrigerated and marinated for up to 24 hours.

 Instructions (Fajitas)

1. Heat a large cast iron skillet over medium-high heat.
2. Add 1 tablespoon of olive oil to the pan. Shake off the excess marinade from the beef, scrape off any garlic and jalapeño to prevent burning, then pat dry with a paper towel. Carefully add steak to the hot pan.
3. Sear without moving the beef until the surface browns, about 2 to 3 minutes. Flip over and cook until the internal temperature reaches 120 to 125ºF (49 to 52ºC) for medium-rare, about 2 to 4 minutes depending on the thickness. Transfer to a cutting board, cover with foil, and allow to rest for 10 minutes before slicing.
4. Add 1 tablespoon of olive oil to the pan. Once hot, add the onions and sauté for 1 minute. Add mushrooms, sauté for 1 minute. Add bell peppers, sauté for 2 minutes.
5. Season with 1/2 teaspoon salt and 1/4 teaspoon black pepper, stir to combine. The vegetables should be crisp-tender.
6. Slice the beef across the grain, on a bias, into thin 1/4-inch thick strips.
7. Combine the beef slices on top of the vegetables with 1/4 reserved marinade.
8. Season with salt and pepper as desired.
9. Garnish with chopped cilantro leaves.
10. Serve the steak fajitas with warmed tortillas and desired toppings.