Prep the onions and tomatoes and salt: Chop the tomatoes, onions into similar size chunks add to a mixing bowl and sprinkle over the salt and mix, leave in a bowl or colander to draw out the excess moisture whilst you prepare the rest of the ingredients.
Prep the remaining ingredients: Measure out the vinegar, sugar & mustard seeds. Roughly chop the raisins, set to one side. Peel and mince the garlic & ginger - add to a small bowl for use later. De-seed and remove the membrane from the red chilli, then finely dice, add to the bowl with the garlic and ginger.
Boil the Vinegar: Add the vinegar and sugar to a large pan and bring to the boil, stirring to dissolve the sugar. Once sugar has dissolved, reduce heat to a simmer.
Prep the apples: Peel, core and dice the cooking apples.
Make the Chutney 'base': Add the sultanas, mustard seeds and apples to the vinegar mixture. Add the garlic, ginger and chilli to the apple mixture and simmer for 10 mins
Add the tomatoes and onions to the Chutney base: Strain the tomatoes and onions in a colander (but don’t rinse), then tip into the pan and return to the boil.
Cook the chutney until thickened: Reduce mixture to a simmer, cook for about 1 hr, stirring occasionally until the mixture is thick and pulpy. After about 1 hour, all of the vinegar should be absorbed by the ingredients and the chutney should have become a thick, soft, semi-syrupy consistency, it should be thick enough to leave a clear trail across the bottom on the pan when a wooden spoon is drawn across it. (The chutney will continue to thicken as it cools.)
Decant into jars: Transfer to warm sterilised jars (see tips, below) and cover with lids & seal.