Clean and wash the aubergines and peel them lengthwise, finger-wide. Leave to stand in salted water for 30 minutes. Peel and halve the onions and cut into half rings. Peel garlic and chop roughly.
Wash parsley, dab dry and chop finely. Cut tomatoes crosswise, briefly boil water over them, peel skin. Cut tomatoes into quarters, remove seeds and dice. Mix onions, garlic, parsley, diced tomatoes and a teaspoon of salt.
Lightly squeeze out the aubergines, cut lengthwise and add the filling. Put olive oil, sugar and 1/2 litre water in a pot. Place the aubergines in it and weigh them down with a plate. Cover and cook for one hour at low heat.
Let it cool down and serve.