Preheat oven to 260F. Line 3 to 4 baking sheets with parchment paper. Prepare 3 pastry bags, 1 large bag and 2 smaller ones. Tip the large bag with a #847 tip; set aside.

Place the egg whites into a very clean mixing bowl. Combine the sugar and cream of tartar together in a small bowl. Turn mixer on to medium speed and add the sugar into the egg whites, whisking at the same time. After adding all of the sugar, turn the mixer to high speed and whisk for 10 to 12 minutes, until egg whites form stiff and glossy peaks. The meringue should look like marshmallow cream.

Add the raspberry extract and whisk for 30 seconds. Divide the meringue between 2 large bowls. Into one bowl, add a few drops of red/pink food coloring and fold the color in.

Transfer the different colored meringues into two separate pastry bags. Cut off the tips and carefully slide the two bags, side by side, into the third pastry bag. Pipe the meringue in a swirl pattern onto prepared baking sheets, leaving 1/2-inch between each cookie.

Bake the meringues in preheated oven for about 1 hour, or until the cookies sounds hollow when tapped. They should come right off of the parchment paper. If your cookies start to brown, open oven door and turn temperature down by 10 degrees. Transfer baked meringues onto cooling racks to cool.

Prepare the lemon buttercream. Cream the softened butter until light and fluffy. Add a few cups of confectioner's sugar and whisk again until fluffy. Zest two large lemons and add the lemon zest to the buttercream. If desired, add a few drops of yellow food coloring.

Keep meringue shells and buttercream separate until ready to serve. Spread a generous amount of buttercream onto one shell and top with a second one. Keep meringue shells in an airtight container. Recipe makes about 25 sandwiches.