Start by slicing the chicken breast into thin strips or cut it in half horizontally. In a mixing bowl, combine the chicken with the fajita seasoning, lime juice, and half of the vegetable oil. Toss well to coat and let marinate for at least 15 minutes.
Heat the remaining vegetable oil in a large skillet over medium-high heat. Add the chopped onion, green bell pepper, and red bell pepper. Sauté for about 5 minutes until tender and slightly caramelized, then remove from skillet.
In the same skillet, add the marinated chicken strips. Cook for about 7-10 minutes, stirring occasionally, until cooked through and browned.
Preheat your oven to 350°F (175°C). Spread tortilla chips in an even layer on a baking sheet. Top with sautéed chicken and veggies, then sprinkle shredded cheddar cheese over the top.
Bake for about 10 minutes, or until the cheese is melted and bubbly. Watch closely to avoid burning the chips.
Remove from oven and top with pico de gallo, sour cream, and guacamole. Add any additional toppings as desired.
