For the curry sauce, peel and finely dice the onion. Heat butter in a pot. Fry the onion until transparent. Sprinkle with sugar and caramelise lightly. Sprinkle with 2 tbsp. curry and sauté briefly.
Add the tomatoes and bring to the boil. Boil down for about 20 minutes while stirring.
Finely dice the cucumbers. Add cucumbers, ketchup and stock to the sauce. Season with vinegar, sambal oelek and salt. Keep the sauce warm.
Heat the oil in a large frying pan. Fry the sausages for 3-5 minutes, turning them until golden brown. Serve with the curry sauce. Dust with curry powder. French fries taste good with it.