Preheat the oven to 325°F.
In the bowl of a stand mixer fitted with a paddle attachment, cream the butter, sugar, vanilla, and lemon zest until light and fluffy. Add the egg yolks and mix to combine.
Whisk together the flour with the salt and add to the butter mixture. Mix just to combine. Scoop the dough into rounded tablespoons balls and press the balls into a lightly greased mini muffin tin. Using a finger or the back of a measuring spoon, gently press the dough about 3/4 of the way up the sides of each cup.
Bake for about 18-20 minutes or until just barely golden. The cookies will puff in the oven. Press them again with the back of a spoon immediately when they come out of the oven.
Cool completely and fill with lemon curd. Garnish with a strip of lemon zest.