Begin by preheating your oven to 400°F (200°C) while you prepare your ingredients. Grab a 9x13 baking dish and lightly grease it with cooking spray or a drizzle of olive oil.

In a large mixing bowl, combine the sliced chicken with olive oil, lime juice, and the homemade fajita seasoning. Let the chicken marinate for about 10-15 minutes.

Once the chicken has marinated, add the sliced bell peppers and onions to the bowl. Toss everything together until the veggies are evenly coated.

Layer half of the marinated chicken and veggie mixture in your prepared baking dish. Add half of the diced tomatoes and sprinkle 1 cup of shredded cheese over the top. Create a second layer with the remaining chicken and veggies, followed by the rest of the diced tomatoes and cheese.

Cover the baking dish tightly with aluminum foil and place it in the preheated oven. Bake for 20 minutes.

After 20 minutes, carefully remove the foil and bake for an additional 10-15 minutes until the cheese is bubbly and slightly crispy.

For an extra touch of perfection, switch your oven to broil and let the casserole broil for 2-3 minutes.

Once your casserole is perfectly baked, remove it from the oven and let it cool slightly. Sprinkle fresh cilantro on top before serving.