Fill your kettle and boil it. Peel and chop the onion. Peel and finely slice the garlic. Peel and grate the turmeric. Trim and chop the rhubarb into 2cm pieces.
Tip the rice into a pan. Pour in 250ml hot water from the kettle. Bring to the boil and cover. Put on a low heat. Simmer for 6 mins till the water is absorbed. Let it steam, lid on, for another 2-3 mins.
Heat a deep frying pan or wok and add 1 tbsp olive oil. Add the onion and garlic. Stir and fry for 4 mins till soft and glossy.
Add the garam masala to the onions and cook for 2 mins. Add the turmeric. Tip in the red lentils and stir thoroughly to coat in the spiced onions.
Pour in 150ml of hot water and stir for 3 mins till absorbed. Add the rhubarb with another 150ml hot water. Add 1 tbsp sugar. Stir and cook for 10 mins till the rhubarb is just soft and the lentils are cooked through.
Grate or pare the zest from the lime. Stir into the yogurt. Juice one half and slice the other half into wedges to serve. Pour the juice into the lentils.
Roughly chop the chervil leaves. Stir half of the chopped chervil through the lentils, save the rest for later. Fluff up the rice with a fork.
Serve the lentil and rhubarb curry with the rice. Top with a dollop of yoghurt and a scattering of the chervil. Pop a lime wedge on the side for squeezing.