1. Wash the lentils in cold water until the water runs clear. (This is essential, otherwise the lentils will get 'scummy'.)
2. Put the Lentils in a post with water. Cover and simmer until lentils are tender. Add more water if necessary.
3. While the lentils are cooking, add the oil to a large skillet or saucepan and carmelize the diced onions.
4. While the onions and lentils are cooking, combine the dry ingredients (curry powder, turmeric, cumin, salt, sugar, garlic, ginger, and if you're using them, curry paste, chilli powder) in a mixing bowl. Mix well.
5. When the onions are cooked, add the curry mixture to the onions and cook over a high heat stirring constantly for 1-2 minutes.
6. Stir in the tomato paste with water (or the tomato puree) and reduce heat, allowing the curry base to simmer until the lentils are ready.
7. When the lentils are tender, drain them briefly (they should have absorbed most of the water, but you don't want the curry to be too sloppy).
8. Mix the curry base into the lentils. Top with a cilantro garnish and serve!