In a large saucepan, heat oil over medium heat. Once thoroughly heated, fry onions until soft, 8-10 minutes. Stir in curry powder and paprika. Fry until fragrant, about 1 minute. Add tomato sauce, sugar to taste, red wine vinegar, and salt.
Increase to high heat. Once boiling, decrease to medium low heat and simmer. Stir occasionally and continue to simmer for 25 minutes, until thickened.
Serve hot over cooked Bratwurst with Brötchen (roll) or Pommes Frites (french fries).