Heat oil in a large pot on medium-high heat. Add onions and saute until carmelized, about 8 minutes. Add ginger and green chili and saute for 1 minute. Add tomatoes, turmeric, cumin, and salt and cook until tomatoes soften, about 5 minutes. Add all remaining vegetables, reduce heat to medium, cover pot, and cook for 10 minutes. Vegetables will cook in their own steam; however, if too dry, add water 1 Tbsp at a time. Add lentils or peas and water and reduce heat to low. Cook for about 30 minutes, until lentils/peas are soft. [Here, the cookbook says to mash with a fork or use a food proessor or hand-blender to lightly puree leaving some vegetable chunks, but I decided to leave all veggies as is]. Add lemon juice, season with salt and pepper and serve.