In a large frying pan, heat the oil over moderately low heat. Add the onion and cook until starting to soften, about 3 minutes. Add the garlic and ginger and cook, stirring occasionally, for 2 minutes longer. Stir in the cumin, coriander, turmeric, paprika, and 1 teaspoon of the salt. Cook until the spices are fragrant, about 1 minute, and then stir in the jalapeños and tomatoes. Add the cream, cinnamon stick, and water. Squeeze the spinach to remove excess liquid and add the spinach to the pan. Bring to a simmer. Cover the pan, reduce the heat, and simmer for 5 minutes.