Wash the lentils in cold water until the water runs clear (this is very important or the lentils will get "scummy"), put the lentils in a pot with water to cover and simmer covered until lentils tender (add more water if necessary).
While the lentils are cooking: In a large skillet or saucepan, caramelize the onions in vegetable oil.
While the onions are cooking, combine the curry paste, curry powder, turmeric, cumin, chili powder, salt, sugar, garlic, and ginger in a mixing bowl.
Mix well. When the onions are cooked, add the curry mixture to the onions and cook over a high heat stirring constantly for 1 to 2 minutes.
Stir in the tomato puree and reduce heat, allow the curry base to simmer until the lentils are ready.
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).
Mix the curry base into the lentils and serve immediately.
