Put the butter in a large pot over medium heat. When it foams, add the beef, and sprinkle with salt and pepper. Cook, stirring frequently, and breaking up any large pieces until it’s no longer pink and brown in places, 5 to 10 minutes. Add the onion and cook, stirring occasionally, until soft and jammy, 5 to 10 minutes.
Add the flour and cook, stirring frequently, until the flour coats the meat mixture and turns golden, 2 or 3 minutes. Add the tomato paste and paprika and stir until fragrant. Pour in 4 cups water, add the Worcestershire sauce and a pinch of salt, and bring to a boil.
Add the noodles, and reduce the heat, so the mixture bubbles gently. Cook, stirring occasionally until the noodles are tender but not mushy, 6 to 10 minutes, depending on their thickness. Remove from the heat and stir in the sour cream, taste and adjust the seasoning, adding more Worcestershire if you like. Serve garnished with the dill.