For the curry ketchup, peel the onion and dice very finely. Heat 1 tablespoon of oil in a pot. Fry the onion in it. Sprinkle with curry and sauté briefly. Add tomato puree and sugar and sauté briefly.
Add the tomatoes, juice and vinegar. Chop the tomatoes. Bring to the boil and simmer for about 10 minutes, stirring occasionally. Season to taste with salt, pepper and curry.
Peel and wash the potatoes and cut them into thick chips. Heat frying oil in a wide pot to approx. 180°C (check with a fat thermometer or hold a wooden stick inside - if bubbles rise, the right temperature has been reached).
Fry the French fries for 2-3 minutes in portions. Lift out each portion and spread out flat on kitchen paper.
In the meantime heat 1 tablespoon of oil in a frying pan. Prick the sausages several times to prevent them from bursting and fry them in the hot oil all around for 8-10 minutes.
Fry the chips a second time in hot frying fat for 3-5 minutes until golden brown. Season the finished French fries with salt and keep warm in a hot oven (approx. 50°C). Arrange the sausages with chips, curry ketchup and mayonnaise.
Dust sausages with curry.