For the eggplant, cut into 1cm slices. Salt well and leave for 1 hour. Wash and pat dry.
Blanch, peel and deseed tomatoes. Cut into 1cm dice.
Heat half the oil in a large frying pan and fry half the eggplant slices to a deep golden brown, taking care not to burn. Remove from pan and drain on paper towel to remove excess oil. Repeat with remaining oil and eggplant. When eggplant is cool enough to handle, roughly chop into 1cm pieces. Add parsley leaves to pan and fry very quickly until crisp (stand back, as it will spit). Remove and add to eggplant.
Reduce heat, then add garlic and cumin to pan. Cook for 2 minutes then add tomatoes. Cook for another 2 minutes then put eggplant and parsley back into pan. Cook for 1 minute, then remove from heat. Add a dash of extra virgin olive oil, lemon juice to taste and a grind of pepper. Check seasoning. Allow to cool.
For the mayonnaise, whisk all the ingredients together and finish with some lemon juice, to taste.
Dice the tuna into ½-1cm pieces. Just before serving, season with extra virgin olive oil, lemon juice, salt and pepper.
Share eggplant salad across four plates. Top with tuna then dollop a spoonful of cumin mayonnaise and drizzle roasted chilli oil around each dish. Garnish with finely chopped chives and serve immediately.