Preheat your oven to 425 degrees Fahrenheit. Spray a 9 by 13 inch casserole dish with cooking spray and set aside.
Bring a large pot of water to a roaring boil. Salt the water. Add in the pasta and cook for 2 minutes less than is indicated on the box.
1 pound bowtie pasta, 1 teaspoon kosher salt
While the pasta is cooking, heat the olive oil in a skillet for approximately 30 seconds. Add the bell peppers, onion, and garlic. Sauté until soft, about 5 to 7 minutes.
2 tablespoons olive oil, 1 yellow bell pepper, 1 red bell pepper, 1 medium red onion, 2 garlic cloves
Stir in the tomato sauce. Season with fajita seasoning. Bring to a low simmer and cook for 5 minutes, you should see just small occasional bubbles.
15 ounces tomato sauce, 2 tablespoons fajita seasoning
Stir in the cooked pasta, chicken, and 1 cup of cheddar cheese. Transfer the mixture to the prepared baking dish. Top with the remaining cheese. Bake for 10 minutes.
3 cups cooked shredded chicken, 3 cups cheddar cheese