In a heavy-bottomed pot, bring the lentils and water to a boil, skimming off any scum that rises to the top. Stir in the turmeric. Cover pot, with lid slightly ajar, and simmer over low heat for 1 1/4 hours, stirring occasionally.
While the lentils are cooking, heat the oil in a frying pan over medium heat. Add the cumin seeds and cook for 3 to 4 seconds, then add the garlic. Once the garlic pieces start to brown, add the onion, cabbage and green chilies. Cook the cabbage mixture, stirring often, until it starts to brown. Stir in 1/4 teaspoon salt. Turn off the heat.
After the lentils have cooked for 1 1/4 hours, add and stir in the tomato, the ginger, and 1 1/4 teaspoon salt. Cover and continue to cook for 10 minutes. Add the cabbage mixture. Stir to mix and allow to simmer uncovered for a few minutes to reheat the cabbage.