Trim and part-peel the aubergines, leaving strips of the skin intact, then dice the flesh.
Peel the tomatoes, squeeze them to release the juice, then dice the flesh.
Place the aubergines and tomatoes with the spices in a pressure cooker and add the herbs and the garlic. Add the water and oil, and season with salt. Mix well, close the lid firmly, cook over a gentle heat for 10 minutes, then remove the lid and let the 'caviar' reduce. If you do not have a pressure cooker, place the ingredients in a heavy-based casserole or saucepan as above, cover, and cook over a gentle heat for 30 minutes. Remove the lid and let the 'caviar' reduce before serving.
Serve garnished with strips of preserved lemon and lemon-marinated olives.