Purchased lemon curd can be substituted for the homemade lemon filling. Lemon curd is a creamy mixture of lemon juice, sugar, butter and egg yolks, cooked until thick. When the curd cools, it's thick enough to use as a spread for baked goods.
Use a spatula or pancake turner to turn the cutout cookies in sugar to coat them, and to transfer them to the cookie sheets.
Both the cookies and the filling can be made ahead and stored separately for several days. For the best texture, assemble the cookies just before serving.