In a large bowl, add the chicken, 1 tbsp oil, fajita seasonings, and lemon juice. Toss to combine the chicken with the seasonings. Refrigerate for about 30 minutes.
Chop the onion and peppers.
In a large skillet over medium-high heat add 1 tbsp olive oil. Sauté the peppers and onions for about 4-6 minutes until slightly cooked. They should be crisp-tender, not overcooked. Remove from the pan and keep warm.
In the same skillet cook the chicken for 5-10 minutes, until no longer pink. Add the peppers and onions back into the pan, toss with the chicken and cook for 2 more minutes.
Serve over low carb tortillas and top with salsa, avocado or any of your favorite toppings.