1. In a large bowl, beat butter, sugar, and salt with an electric mixer on medium speed until fluffy and well blended. Beat in egg yolk, vanilla, and lemon peel Reduce speed to low and beat in flour until just combined. Divide dough into quarters and wrap each in plastic wrap. Chill at least 1 hour or up to 2 days.
2. Heat oven to 350 degree F. Spray 2 large cookie sheets with nonstick cooking spray. On a lightly floured work surface, roll one disk of dough to 1/8-inch thick. Using a 2-1/2-inch cookie cutter or straw, cut out the centers of half of these cookies, rerolling and cutting out the scraps. Place cookies half an inch apart on prepared sheets. Bake until evenly golden brown, about 6 to 8 minutes. Transfer cookies to wire racks to cool completely. Repeat with the remaining dough.Make filling::
3. In a large bowl, beat all ingredients with an electric mixer until blended. When cookies are completely cool, spread 1/2 teaspoon filling on each cookie bottom, and top with a cut-out cookie. Makes 30 cookies.To Make These Goodies a Gift::
4. Find old-fashioned glass jars at tag sales or at kitchen supply stores. Mason jars used for canning and preserves will also work. Stack the cookies flat in two rows, to fit as many as possible. Make sure the cookies are completely cooled, so they don't stick together.