Finely chop the onion, press the garlic, finely grate the ginger. Sauté in olive oil for approx. 5 mins. Pour in the apple juice and bring to the boil, reduce to approx. half the amount. Add the tomatoes, vinegar and sugar, bring to the boil, then reduce the heat and simmer over a low heat for approx. 30 mins. Season, puree, allow to cool.