In a large skillet over medium heat, melt 3 tbsp of butter. Add the onion and garlic to the pan. Sauté until onion is translucent and garlic is fragrant.
Add red wine vinegar to the pan and mix in with onions and garlic.
Add sliced kielbasa to the pan and sauté until slightly browned.
Add remaining butter, cabbage, paprika, salt and pepper. Toss to mix all ingredients together and coat the cabbage with butter and seasonings.
Saute until cabbage is wilted and slightly browned.
Top with fresh parsley and crushed red pepper flakes before serving.