Chop the onion finely and fry in a little olive oil until translucent. Slice the aubergine lengthwise into 1/2 cm slices. Add to the onions and fry lightly until coated well with the olive oil (add more olive oil if necessary). Add approx half a tube of tomato paste into the mix and stir well. Cover with water, add the juice of a lime and season well with the salt & pepper. bring to the boil then reduce to a low heat and simmer minimum 30 minutes until the aubergine is very tender and the sauce is thick and tasty. If you have time, let it simmer another 15-30 minutes for an even richer flavour. if the sauce is still watery, add more tomato paste to thicken. Taste and add more lime juice, salt & peper to taste.