Preheat the oven to 180C/350F/gas 4.On a chopping board, cut the aubergines in half lengthways.Score the flesh sides in a crisscross pattern, making sure you don’t cut through the skins.Drizzle with 2 tablespoons olive oil, then toss to coat.Arrange on a baking tray, flesh-side facing up, then bake in the oven for around 45 minutes, or until soft.Using oven gloves, remove the aubergine from the oven, then leave aside to cool.Peel and roughly chop the garlic, then place in a food processor.Add the tahini, chilli powder (if using), cumin, 2 tablespoons extra virgin olive oil and the aubergine, discarding the skin.Cut the lemons in half. Squeeze in the juice, using your fingers to catch any pips.Secure the lid and blitz to a nice thick dip.Have a taste and add a tiny pinch of salt and pepper, if you think you think it needs it.Transfer to a bowl, to serve.