Preheat the oven to 220 degrees C (428 Fahrenheit) or heat up the grill.
Place the aubergines and peppers on a roasting tray / on the grill and roast until the flesh is soft, this might take about 45 minutes in the oven, on the grill it depends entirely on the heat. The peppers will be ready a lot quicker, so do keep an eye on them.
When the aubergines and peppers are charred and the flesh is soft, allow them to cool, then peel, remove the seeds from the peppers and chop the aubergines finely. The peppers can be left in bigger chunks, if you prefer.
Next, peel and chop the onions.
Heat up the oil in a pan, add the onions and fry until soft.
Chop the tomatoes and add them to the pan, stirring until they become mushy.
Add the aubergines and peppers and stir well.
Mix in the vinegar, and season with salt and pepper.
When the sdip starts to bubble, turn off the heat and leave to cool slightly.
It can be served either hot or cold.