In a medium saucepan, combine 2 cups of water, the onions, garlic, ginger, tomatoes, chile, if using, and the lentils. Bring to a boil over medium-high heat. Skim any scum from the surface. DO NOT ADD SALT YET; it will toughen the lentils, thereby lengthening their cooking time. Lower the heat, cover the pot with a lid and gently simmer until the lentils are tender, almost translucent, and almost falling apart, about 30 to 40 minutes.