Chop onions, garlic, and rhubarb.
Heat the tablespoon of vegetable oil in a large saucepan over a medium-high heat. Pour in the chopped onions and garlic. Fry for about 2-3 minutes until the onions are nice and soft.
Add the cup of sliced rhubarb into the frying pan along with the 2 tablespoons of garam masala, 2 teaspoons of cinnamon, 2 teaspoons of caster sugar and ½ teaspoon of cayenne pepper. Cook for around a minute, stirring well to combine.
Tip in the 1.5 cups red lentils and 3.1 cups of vegetable stock. Bring the pan to the boil, then turn down to a simmer, cover and cook for around 13 - 15 minutes until the lentils are cooked and the stock has reduced to a thick sauce.
Start Rice
Remove the pan from the heat and season to taste. Then stir in the 5 cups spinach and 2 cup chopped coriander. Stir the spinach and coriander until they have wilted sufficiently.
Serve the curry immediately. I recommend eating it with fluffy pilau rice or a fresh naan. Alternatively it can be eaten on its own as a semi-dhal. Enjoy!
