Chop an onion into fine cubes and stir in a bowl with the quark, horseradish and the tomato ketchup.
If you don`t like horseradish and onions, you can omit them, it tastes good without! Season the dip with salt, possibly also season with horseradish and tomato ketchup.
The dip is ready very quickly and goes very well with barbecues. It tastes good with meat, sausages, but also just with toast.