Heat the oil in a large pot over medium heat, then sauté the onions, ginger, and garlic until tender but not browned. Add the cumin, turmeric, coriander, paprika, chili powder, and garam masala and stir constantly for about 30 seconds, until the spices are fragrant. Stir in the tomato puree, tomato sauce, and 1 ¼ cups of water, then bring to a boil and cook for about 5 minutes. Pour in the cream.