1. In a medium mixing bowl, use an electric mixer to beat butter and sugar together until light and fluffy.
2. Mix in egg yolks, vanilla and zest.
3. In a separate small mixing bowl, mix together flour and salt; add to the bowl with the butter mixture and mix until no traces of flour remain.
4. Divide dough in half; shape each half into a rough disc shape. Wrap tightly in plastic wrap; refrigerate for 1 hr. or until firm.
5. Preheat oven to 350°.
6. On a cold work surface sprinkled lightly with flour, use a rolling pin dusted lightly with flour to quickly roll out 1 disc of dough to an even ⅛" thickness (keep remaining dough refrigerated until ready to roll).
7. Cut dough with cookie cutters, rerolling scraps; place 1" apart on parchment-lined baking sheets.
8. Roll and cut remaining disc of dough.
9. Bake in preheated oven until edges are lightly browned (10-12 min.), rotating and turning pans halfway through.
10. Remove from oven; let cookies rest on sheet pans for 2 min., then transfer to a wire rack to cool completely.
11. Unfilled cookies may be stored in an airtight container in the refrigerator for up to 5 days. When ready to serve, dust cookies with confectioners' sugar. Spread curd on the bottom of half the cookies, spreading it lightly at the edges; top with remaining cookies, bottoms down. Garnish as desired. 

Tasty Tips:

• The yield on this recipe depends on the size and shape of the cookie cutter(s) used. A cutter roughly 2" wide will yield approx. 2 dozen cookies.
• If dough is made well in advance and is fully chilled, bring to room temperature for 1 hr. before rolling.
• If dough gets too warm, it may be a good idea to put the cut cookies into the fridge for 20-25 min. before baking.