Wash the mung beans and remove any stones (no need to soak). Transfer them to a medium size saucepan. Add 6 cups of water and a pinch of baking powder. Bring to a hard boil. Reduce the heat and simmer until the beans are tender, about 30 minutes. *see note 1
While the mung beans are cooking, heat the coconut oil in a large pot. Saute the onions for 3-4 minutes. Add, the cumin, coriander, turmeric, chili flakes,salt and pepper. Saute for a further minute.
Add the garlic and ginger and saute for one minute more. Tip in the tomatoes and coconut milk and bring the mixture to a boil. Reduce the heat and simmer for 10 minutes.
Stir in the lemon juice and garnish with chopped coriander and coconut yogurt.
If you find that the water is evaporating too quickly, simply add a bit more until the mung beans are cooked.