Heat 1 cm/1/2" oil in a frying pan (skillet).
Fry the aubergine slices in batches for 3-4 minutes over a medium to high heat until golden brown, topping up the oil between batches as necessary. Drain on kitchen paper and set aside.
Add 1 tablespoon of oil to the pan and fry the harissa paste and chopped tomato for 2 minutes. Add the aubergine slices, stir gently and set aside to cool before serving.