In a bowl, combine shrimp with paprika, garlic powder, ½ teaspoon salt, and ½ teaspoon pepper. Set aside.
Mince the garlic, grate the Parmesan, chop the sun-dried tomatoes, and chop the basil leaves.
Boil the rigatoni al dente in salted water, according to the package directions. Reserve 1 cup of the pasta cooking water, then drain.
In the meantime, heat oil and butter over medium-high in a large skillet. Place shrimp in a single layer, and sear for 1 minute per side. Remove from the skillet into a clean bowl.
Add garlic, and sauté for 1 minute over medium-low. Then add the sun-dried tomatoes, Italian seasoning, and the remaining salt and pepper. Cook for 1 minute more. Add flour, and stir until incorporated. Deglaze with chicken broth, and simmer for 2 minutes while scraping up the brown bits on the bottom of your skillet with a wooden spoon.
Stir in tomato paste, and bring to a boil. Add the pasta to the pan and toss until the pasta finishes cooking about 2 minutes. Next, add lemon juice and basil. Finally, stir in Parmesan.
Toss pasta with shrimp. Finish off with chili flakes.