Preheat the oven to 180C/350F/Gas 4.
For the lamb, heat the olive oil in an ovenproof frying pan until smoking. Season the lamb leg steak with salt and freshly ground black pepper, then sear in the pan for 3-4 minutes on each side, or until browned all over. Add the lemon wedges to the pan and transfer to the oven for 10-12 minutes, or until the lamb is cooked to your liking.
For the lentils, heat the oil in a pan and gently fry the onion and garlic for 3-4 minutes, or until beginning to soften, then stir in the cumin seeds and ground turmeric.
Pour in the wine, then reduce the heat and simmer for 1-2 minutes. Stir in the double cream, lentils and season with salt and freshly ground black pepper. Leave to simmer for another 5-6 minutes, until the liquid starts to reduce and the lentils are heated through.
To serve, spoon the creamed lentils onto a serving plate and place the lamb steak on top. Garnish with the fresh coriander leaves.