Slice the aubergines lengthways, keeping them joined at the stem.
To make the marinade, mix the turmeric and lemon juice together in a bowl. Season with salt and rub the aubergines all over with the marinade. Place the aubergines in a large shallow dish, then cover and set aside for 30 minutes.
Heat enough oil for deep-frying in a kadhai or deep, heavy-based pan to 180°C / 350’F, or until a cube of bread browns in 30 seconds. Carefully lower the aubergines into the hot oil and deep-fry for about 2-3 minutes, or until cooked, working in batches if necessary. Remove with a slotted spoon and drain on kitchen paper (paper towels).
Put all the ingredients for the spice paste in a bowl, add 4 tablespoons water and mix well.
To make the sauce, put the tamarind pulp in a pan, add 125ml / 4 1/2fl oz (1/2 cup) water, bring to the boil, then reduce the heat to low and simmer for 5-7 minutes until reduced by half. Strain through a sieve (strainer), discard the fibers in the sieve and, set the extract aside.
Heat the oil in a heavy-based pan over medium heat, add the cloves and cinnamon and stir-fry for a few seconds, then add the spice paste and stir-fry for about 2 minutes, or until the oil separates out.
Add the pureed tomato and continue frying for 2-3 minutes, then add the tamarind extract and fry for about 1 minute, before adding the fried onion paste. Continue to cook until the oil separates out and rises to the top.
Pour in 250ml / 8fl oz (1 cup) water, then bring to the boil, reduce the heat, and simmer, stirring occasionally, until the sauce is a thin consistency.
Lower the aubergines carefully into the sauce and simmer for a further 5 minutes. Remove from the heat and adjust the seasoning, if necessary.