Hanukkah Sugar Cookies

Name: Hanukkah Sugar Cookies
Prep time: 30 min
Cook time: 10 min
Total time: 40 min
Cuisine: Israeli
Ingredients: ¾ cup unsalted butter (softened (not melted)); ¾ cup granulated sugar; 1 egg; 1 teaspoon vanilla extract; 1 teaspoon lemon zest; 2 1/4 cups all-purpose flour; 1/2 teaspoon baking powder; 1/2 teaspoon salt; 2 egg whites (at room temperature); 1/2 teaspoon cream of tartar; 4 cups confectioners' sugar; 1 tablespoon or more water (room temperature)