In a pot over medium-high heat, place lentils in about 3 cups (750 mL) of cold water and bring to a boil, adding half of the garlic and ginger to the pot. Lower the heat and continue to cook on medium until lentils are cooked. (Don’t overcook or they will end up like mush!)
While the lentils are cooking, in another small pan, heat the oil on medium-high heat and add onions; cook until transparent, golden and soft. Add remaining ginger and garlic, thyme, curry leaves, chilies and tomatoes. Cook for a few minutes then add curry powder and stir. Lower heat and cook for another 5 minutes or so, stirring occasionally.
Once lentils are cooked, add them to the onion mixture. Add water or stock and spinach, and cook over medium to low heat for about 15 minutes.
Add fresh chopped coriander and salt. Serve hot with rice or have as soup with bread.