Preheat the oven to 200°C, 400°F, Gas 6.
Pierce the aubergines all over with a sharp knife, place on a baking sheet and roast in the oven for at least 45 minutes, or until blackened and collapsed. Remove from the oven and allow to cool.
Slice each aubergine in half and scoop out the pulp. Finely chop the pulp and squeeze to remove excess liquid, then place in a bowl. Finely dice the tomatoes and add to the aubergine pulp with the onion and garlic. Add lemon juice to taste and stir in enough olive oil to make a loose consistency. Season and stir through the parsley before serving.