Given the task definition and input, reply with output. In this task, you will be presented with the directions of a recipe separated by "," and have to fill in the "___" which is a step that is missing from the recipe.

Preheat oven to 325.,Sift flour, sugar, baking powder and 1 teaspoon salt into bowl.,Make well in center.,Add oil, egg yolks, 3/4 cup cold water, vanilla and lemon rind.,Beat until smooth.,Beat egg whites and cream of tartar until stiff peaks form (do not underbeat).,______,Do not overmix.
Pour egg yolk mixture gradually over egg whites; fold gently until blended.