Preheat oven to 350ºF (177ºC). Spray a 9 X 13-inch baking dish lightly with nonstick cooking spray. Set aside.
Cook pasta (12 ounces) according to package directions. Drain pasta and dry the pasta pot.
Meanwhile, in a large bowl, combine all the dry rub ingredients. Add the cubed chicken (1 1/2 pounds) and toss to evenly coat. In a large skillet, heat 1 tablespoon of the olive oil over medium-high heat until it begins to shimmer. Add the chicken in a single layer and cook without stirring, until one side is browned, about 2 minutes. Turn the chicken and brown the other side. Remove the chicken to a plate and set aside.
Add the remaining olive oil and heat until shimmering. Add the bell peppers (2), onion (1), and jalapeno (1), and cook on medium heat until soft, about 7-10 minutes. Turn the heat down to low and add the garlic (4 cloves), and continue to cook 1 minute more. Remove all the cooked veggies to the chicken plate and set aside.
Add butter (1/2 cup) to the skillet and melt over medium heat. Whisk in flour (1/2 cup) and continue to cook for 1 minute. Remove skillet from heat and slowly whisk in milk (4 cups). Return to medium heat and cook until the mixture thickens and begins to bubble, stirring constantly. Reduce the heat to low and stir in well-drained tomatoes (1 can), Worcestershire (1 teaspoon), salt (1 1/2 teaspoons), pepper (1/2 teaspoon), and 2 cups shredded Jack cheese.
Add drained pasta back to dried pasta pot and combine with sauce. Stir in chicken and veggies and pour into prepared baking pan. Sprinkle remaining 2 cups of shredded Jack cheese over casserole. Bake in preheated oven for 25-30 minutes or until casserole is bubbly and cheese is melted and golden brown
Notes
Pasta: I like to use egg noodles in this chicken fajita pasta recipe because there’s lots of prime real estate to sop up all that yummy cheese sauce. You should cook your pasta al dente since it's going into the oven afterward. This helps ensure it doesn’t come out mushy.
Salt The Pasta Water: Also, don’t forget to salt your pasta water. I typically use 1-2 tablespoons per gallon of water. The pasta will absorb the salty water as it cooks giving your chicken fajita pasta recipe even more flavor.
Chicken: When you cook the chicken tenderloin pieces with the dry rub on them, you’re essentially searing in all the awesome flavors rather than cooking it all the way through. Using a heavy-bottomed skillet will distribute heat more evenly and help prevent burning.
Be careful not to overcrowd your pan, either. You may have to cook more than one batch. Overcrowding prevents heat from circulating properly so the food can’t cook evenly.
Veggies: Sautéing your veggies is vital to your chicken fajita pasta recipe. It helps combat bitterness and brings out their sweeter more mellow flavors. This helps take the dish to the next level creating sweet robust flavors.
Roux – You probably know that the roux is the base for your cheese sauce. It's important to cook the flour and butter for just a minute so your sauce doesn’t taste like flour. You’ll also want to remove the roux from the heat while you whisk in the milk, stirring constantly until all the lumps are gone.
Queso Sauce – As you transform the roux into queso sauce, you’ll want to continue stirring constantly so it doesn’t burn on the bottom. The sauce will thicken as it bubbles gently, and you can add the remaining ingredients once the desired consistency has been reached.