Lemon Sandwich Cookies are a light, buttery slice and bake cookie with a bright lemon flavor, they are tender, not overly sweet, with a delicious sweet-tart lemon-cream frosting sandwiched between. These might possibly be my favorite cookie.
In a large mixing bowl cream the butter, on medium-high speed 2-3 minutes. Add sea salt and powdered sugar, beat for about 2-3 minutes until light and fluffy. Add vanilla and lemon zest, scraping down sides. Mix on low just until incorporated.
Sift in all-purpose flour and cornstarch into the dough, mix on low until just combined. Divide dough up into 2-3 sections. Place one at a time on a piece of plastic wrap, shape the dough into desired shape. Square or round, or whatever shape you desire, see post for how to.
Wrap in plastic wrap; refrigerate for at least 30-60 minutes, longer if needed. Dough should be firm.
Preheat oven to 300° and line cookie sheet with parchment paper.
Remove mixture from fridge once firm, slice into generous ⅛ slices, like a pat of butter. Place on cookie sheet close together, they won't spread.
Bake at 300 for about 20 minutes until cookies are very lightly golden at the edges. Cool for 2 minutes on the baking sheet, then carefully move to cooling rack, cooling completely.
Lemon-Cream Frosting
Cream butter until light and fluffy, 2-3 minutes. Add powdered sugar and zest, cream additional 2 minutes until light and fluffy.
Slowly add lemon juice until desired tartness and consistency. Spoon scant teaspoon of frosting onto cooled cookie slice, place matching cookie on top.
Place sandwich cookies in airtight container or freeze until ready to eat. If desired dust with a little powdered sugar.