In a large saucepan heat the olive oil, garlic and ginger. Cook until garlic and ginger are aromatic. Add the onion, ½ teaspoon of salt and ¼ teaspoon of pepper and sauté until onions are translucent, about 4 minutes. Add the carrots, celery and sweet potato and another ½ teaspoon of salt and ¼ teaspoon of pepper and sauté on medium heat until all of the vegetables are tender, about another 5 minutes.
Add the can of tomatoes, curry powder, cumin, turmeric, paprika and cinnamon, lentils and stir to coat vegetables and lentils. Pour in the vegetable broth and stir. Increase the heat to high and bring to a boil, stir and then decrease the heat to low and simmer for 20 minutes with a lid on. Remove the lid, add water and simmer for another 15 minutes, without a lid. Turn off the heat, taste and add salt and pepper as needed.