INGREDIENTS
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1 1/2 cups all-purpose flour 1 teaspoon cream of tartar 1 teaspoon baking powder 1/2 teaspoon baking soda 1/4 teaspoon salt 1/2 cup (1 stick) unsalted butter, room temperature 3/4 cup granulated sugar 1 large egg 2 teaspoons vanilla extract 3/4 cup (