Make the meringues – Position racks in the top and bottom thirds of the oven and heat the oven to 200°F. Line 2 large heavy-duty baking sheets with parchment.

In a food processor, process the sugar until very fine, about 45 seconds. Add the confectioners’ sugar and salt and pulse until well blended, about 15 seconds.

In a stand mixer fitted with the whisk attachment, combine the egg whites and cream of tartar. Begin mixing on medium-low speed until frothy. Increase the speed to medium high and beat until the whites form soft peaks, about 2 minutes.

Continue beating while gradually sprinkling in the sugar mixture. When all the sugar is added, increase the speed to high and whip until firm, glossy peaks form, about 3 minutes. Add the vanilla bean paste and extract and beat just until blended, about 10 seconds.

Spoon the meringue into a large pastry bag fitted with a large star tip. Holding the pastry bag perpendicular to a lined baking sheet, pipe small flat disks about 1-1/4 inches in diameter and no higher than 1/4 inch, spaced about 1/2 inch apart. As you pipe, lift the tip up to form a cute little peak.

Bake the meringues for about 30-35 minutes. Open the oven door slightly, then continue baking for about 35-40 more minutes, until dried and crisp but not browned. Turn off the oven and leave the door shut; let the meringues sit in the oven until cool, about 1 hour. Remove from the oven and gently lift the meringues off the parchment. Note: Unfilled meringues will keep in an airtight container at room temperature for about 3 weeks.

To make the lemon curd - Melt the butter in a medium saucepan over medium heat. Remove the pan from the heat and whisk in the sugar, lemon juice, vanilla bean paste, extract, zest, and salt. Whisk in the yolks until well blended.

Cook over medium-low heat, whisking constantly, until the mixture is thick enough to coat the back of a wooden spoon or spatula, about 10 minutes.Do not allow the mixture to boil. Another way to test is to pour a few drop on any surface and run your finger through it. If it doesn't come togetherm then its ready.

Strain the curd into a clean bowl and cover with plastic wrap, pressing the plastic onto the surface to keep a skin from forming. Let cool at room temperature; then refrigerate until completely chilled.The curd will keep for up to 3 weeks in the refrigerator.

Assemble the cookies - Arrange half of the meringues bottom side up on a work surface. Spoon about 1 tsp of lemon curd onto each meringue shell. Gently press the remaining meringues onto the curd, bottom (flat) side down. The filled cookies can be prepared and kept at room temperature up to 2 hours before serving. Note: These cookies become softer the longer they sit, but that's not necessarily a bad thing.

Yield: About 40 sandwich cookies

Adapted from: Fine Cooking