Lightly brown the onion in hot butter in a large heavy skillet.
Blend in flour, paprika, and salt.
Heat until bubbly.
Stir in the broth.
Bring to boiling; cook and stir 1 to 2 minutes.
Remove from heat.
Stirring vigorously, add a mixture of sour cream and tomato paste in very small amounts.
Gently mix potatoes into sauce and cook over low heat stirring 3 to 5 minutes, or until thoroughly heated (do not boil).