Blueberry Lemon Tart

I've been using this crust a lot this summer, because people love it so much. I'll probably find a dozen new ways to fill it as the fall goodies come into season. This version was made for a 14-person dinner party some friends of mine and I threw at my apartment a couple of weeks ago. I thought the tart had all been eaten before anyone got a photo, and just got this photo today. Good thing, too, cause now I can share the recipe with you, internets.

Shortbread Pastry Tart Crust
1 3/4 sticks of unsalted butter, slightly softened
1/3 cup confectioner's sugar
1 egg yolk
1 1/4 cup flour
1 tablespoon buttermilk*

In a medium or large bowl, mix the butter and sugar with a hand mixer on low. Add the egg yolk and beat in until combined, then mix in half of the flour. Add the other half of the flour, then the buttermilk. Lay a cookie-sheet-sized sheet of wax paper out and dump the dough onto the center of it. Place another sheet of wax paper on top and flatten to about 1/4" thick. Set this on a cookie sheet and freeze for about 20 minutes.
Remove the dough from the freezer and let it rest a minute before peeling off one layer of paper. Gently roll the dough around a rolling pin and remove the backing, then carefully unroll it over the tart pan. Press it into place and put it back in the freezer for an hour. Preheat the oven to 350º. Bake the tart in the middle of the oven for 20-25 minutes or until golden around the edges. I remove it from the oven halfway through and press a round cake pan into it to create a nice shape. (This can also be achieved with pie weights, or by lining the tart with parchment or aluminum foil and filling it with uncooked rice.) While the tart shell is baking, start the lemon curd. When the shell is lightly browned around the edges, remove from the oven but do not turn it off. Let cool 5 minutes or so before filling.

Blueberry Lemon Curd
grated zest of two lemons
2/3 cup sugar
1/4 cup lemon juice
4 tbsp (1/2 stick) butter at room temperature
2 large eggs
pinch of salt
about 1 1/2 cups blueberries

Bring about 1" of water to not-quite-simmering in a sauce pot. In a metal bowl, mix the lemon zest, sugar, and butter, blending with a hand mixer until creamy. Add the eggs one at a time. Mix in the lemon juice and salt, then place the bowl over the [almost] simmering water with the heat on low. Stir continuously with a wooden spoon until the curd has thickened enough to coat the back of the spoon, about ten minutes, then remove from heat.
Pour the curd into the tart shell and smooth it out. Cover the top entirely with blueberries. Place in the center of the oven and bake until the blueberries begin to burst and the crust browns. Refrigerate at least one hour before serving so the curd can solidify.