The best replacement for cream of tartar is baking powder.

The best alternatives to cream of tartar are rated as following:
★★★★★  baking powder
★★★  cornstarch
★★  tartar sauce
★★  baking soda
★★  tartaric acid
★★  meringue powder
★  alum
★  citric acid
★  xanthan gum
★  arrowroot

Your alternative for cream of tartar is not listed? Suggest!
Speaking about cream of tartar, one probably shouldn't forget about baking soda.

Other search terms related to cream of tartar and their ratings are:
★★★★★ baking soda
★★★★★ baking powder
★★★★ meringue
★★★ egg whites
★★ whipped cream
★ sulfur
★ whipping cream
★ buttermilk
meringue powder
tartaric acid
You have in mind a companion for cream of tartar and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of cream of tartar in all years. Click on graph for more.
cream of tartar
baking powder
cornstarch