First Step: Dice 1.5 lbs chicken tenderloins into bite-sized pieces. In a bowl, season the diced chicken with 1 tablespoon olive oil, 1.5 tablespoons Italian seasoning, 1 teaspoon salt, and freshly ground pepper. Toss to coat evenly. Preheat a large pot of salted water for the pasta so it will be ready when the sauce is finished.

Second Step: Heat an oven-safe skillet over medium heat and add 2 tablespoons olive oil. Add the seasoned chicken in a single layer and cook for 4-5 minutes per side on low to medium-low until cooked through and lightly browned. The internal temperature should read 165°F. Remove the chicken from the skillet and set it aside on a plate. Keeping the chicken hot helps it stay juicy when you add it back in later.

Third Step: Lower the heat to medium-low. Melt 2 tablespoons butter in the same skillet. Add 1 medium diced yellow onion and sauté for 2-3 minutes until translucent. Stir in 4 minced garlic cloves and cook for about 30 seconds until fragrant but not browned. Pour in 3 cups whole milk slowly while stirring to combine with the pan drippings and butter. Add 2 teaspoons Cajun seasoning, 1 teaspoon red pepper flakes if using, and season with salt and pepper to taste. Stir in 8 oz drained sun-dried tomatoes and 1.5 cups bite-sized broccoli florets, then simmer gently for 5 minutes until broccoli is tender-crisp. Keep the heat low so the milk does not boil to avoid curdling.

Fourth Step: While the sauce simmers, cook 10 oz rigatoni in the boiling salted water to al dente, usually 1-2 minutes less than the package recommends. Reserve a cup of pasta water before draining; the starchy water is useful to thin the sauce if needed.

Fifth Step: Return the cooked chicken to the skillet and stir in the drained rigatoni. Add 2 cups baby spinach and stir until it wilts into the warm sauce. Mix in 1/3 cup prepared pesto, folding everything together so the pesto coats the pasta and chicken evenly. If the sauce seems too thick, add a splash of reserved pasta water until you reach a creamy consistency.

Final Step: Preheat the oven broiler on high. Sprinkle 1.5 cups shredded mozzarella cheese and 1 cup parmesan cheese across the top of the pasta in the skillet. Place the skillet under the broiler for 3-5 minutes until the cheese melts and turns golden brown. Watch closely to avoid burning. Let the bake rest for 3-5 minutes before serving so the sauce sets slightly and the pasta is easier to portion. Serve hot with an extra sprinkle of cracked pepper or a drizzle of olive oil.