Make and assemble the lasagne a day ahead; chill. Bring to room temperature before baking. Can be frozen – defrost, then bake as below. Preheat the oven to 200°C, fan 180°C, gas 6. Halve the tomatoes and place, cut-side up, on a large baking tray. Season, then roast for 45 minutes. When they are ready, take them out of the oven and set aside. Reduce the oven temperature to 180°C, fan 160°C, gas 4. Meanwhile, trim and thinly slice the aubergines, then halve the rounds.