Prepare the rice according to the package directions.
Prepare the kielbasa:
Meanwhile, slice the kielbasa into thin slices. Heat the kielbasa slices in a large skillet over medium-high heat for about 10 minutes until the slices are sizzling and browned at the edges.
Transfer the cooked kielbasa slices to a plate and hold them aside.
Make the sauce:
Add the butter to the skillet, and heat it over medium heat until melted.
Quickly stir in the flour, smoked paprika, garlic powder, salt, and pepper. Stir this roux continuously over medium heat for about 30 seconds. Pour in the milk and whisk to combine it with the roux.
Bring the mixture to a simmer over medium heat, stirring constantly. As soon as the mixture begins to simmer, and it just begins to thicken, remove the pan from the heat.
Stir in the shredded cheese until it is melted. Then stir in the sour cream.
Serve the dish:
Place portions of the rice and kielbasa on serving plates, and top each with the Cheddar cheese sauce.
Serve immediately. Makes 6 servings.
Notes
Feel free to use a different variety of rice if you wish.