Wash the tomatoes, carve them crosswise, add boiling water and remove the skin. Peel onions and cut into slices. Peel and halve garlic. Rinse Romarin twigs.
Put tomatoes, onions, garlic and rosemary twigs in 4 thoroughly cleaned glasses. Bring vinegar, 1/4 litre water, sugar, salt, cloves and peppercorns to the boil, stir in the preserving aid and pour over the tomatoes.
Let glasses cool down, then close them.