As squash bakes, in medium-sized saucepan, heat oil over medium. Add onion, carrot, and 1/4 tsp salt; heat until vegetables are softened; about 5 minutes. Add garlic and gingerroot; heat for 1 minute. Stir coriander, turmeric, cayenne, and black pepper into pan and heat for 30 seconds. Place lentils, tomatoes, and 2 1/2 cups water in pan, bring to a simmer, and cook until lentils are tender, stirring a couple of times, about 15 minutes. If needed, add additional water to pan during cooking.