Prepare the Chicken - For chicken breasts thicker than ½-inch, cut them into thinner cutlets. Use a chef’s knife to cut them in half horizontally to yield four thinly sliced pieces.
Make the Marinade - In a large bowl, whisk together lime juice, ⅓ cup olive oil, chopped cilantro, jalapeno, garlic, soy sauce, lime zest, salt, cumin, paprika, and black pepper—reserve ¼ cup of the marinade.
Marinate the Chicken - Place the meat in the marinade, turning to coat. Allow it to sit for 15 minutes, flipping over halfway through. Do not marinate over 15 to 20 minutes, or the texture will become dry and mushy.
Cook the Chicken - Heat a large cast iron skillet over medium-high heat. Once hot, add 1 tablespoon of olive oil. Shake off excess marinade, making sure there's no garlic sticking to the meat—sear without moving for 3 minutes. Flip and cook until the internal temperature reaches 160 to 165ºF (71 to 74ºC), about 3 to 5 minutes, then turn off the heat.
Slice the Meat - Transfer the chicken to a cutting board and slice it into ½-inch thick pieces. Cover with foil to keep warm.
Cook the Vegetables - Use the same pan to cook the chicken. Turn the heat to medium-high and add 1 tablespoon olive oil to the pan. Add the onions and bell peppers. Saute until vegetables are crisp-tender, 3 to 4 minutes.
Finishing the Dish - Add the sliced chicken and ¼ cup of the reserved marinade to the pan. Stir to combine, cook until meat is warmed through, 1 to 2 minutes. Add more salt and pepper to taste.
To Serve - Serve immediately while still hot, along with warmed tortillas and toppings if desired.
Notes
Serving Size: 1 tortilla plus chicken fajita filling
Make it Gluten-Free and Whole-30: Use gluten-free tamari or coconut aminos instead of soy sauce. Enjoy with cassava flour tortillas.
Storing: Cool completely and store in an airtight container for up to 5 days.
Reheat: Cover and reheat in the microwave on the high setting in 30-second intervals until hot.