Gluten Free Japanese Cheesecake

basic gum-free gluten free flour blend (36 grams superfine white rice flour + 12 grams potato starch + 6 grams tapioca starch/flour)

xanthan gum (recommended, but optional)

cornstarch

egg yolks, at room temperature

+ 2 1/3 teaspoons) milk

unsalted butter, chopped

kosher salt

cream cheese, at room temperature

freshly squeezed lemon juice

egg whites (about 6 ounces), at room temperature

cream of tartar

granulated sugar