Our Cream of Tartar by Frontier Co-op Cream is naturally dairy-, gluten- and grain-free, and contains only one ingredient: tartaric acid. It's also kosher and imported from Spain.
Regarding baking, cream of tartar acts as a leavening agent in Paleo- and GAPS- friendly cakes, quick breads and souffles when combined with baking soda and water. An essential ingredient in Snickerdoodle cookies, it also aids in stiffening egg whites - just add a pinch of cream of tartar while whipping.
Because of its acidity, cream of tartar can be combined with alkaline baking soda to make Paleo baking powder, as commercial baking powders aren't Paleo.