Bring a large pot of salted waterto a boil. Cook noodles until tender; drain and return to pot. Stir in butter; cover and set aside.
Meanwhile, in a medium bowl, combinepork with 1 tablespoon paprika; season with salt and pepper, and toss to coat. In a large skillet, heat 1 tablespoon oil over medium-high; cook pork, tossing occasionally, until lightly browned on all sides, 3 to 5 minutes.
Transfer to a plate (reserve skillet).
Return skillet to stove; reduce heat to medium.
Add remaining tablespoon oil and onion; cook until onion is soft, 4 to 5 minutes.
Add pork, remaining tablespoon paprika, tomatoes with their juice, and 1/2 cup water; bring to a boil. Reduce to a simmer; cook, until sauce is slightly thickened, breaking up tomatoes with a spoon, 2 to 4 minutes.
Remove skillet from heat, and stirin sour cream; season with salt and pepper.
Serve paprikash over noodles, garnished with parsley, if desired.