Step 1

To a food processor, add the flour, unsalted butter, and icing sugar. Pulse until you get a crumbled mixture similar to bread crumbs. Add the egg yolk and cold water, then pulse until the mixture resembles a dough and pulls away from the sides of the food processor bowl.

Step 2

Brush a 9" tart pan (with a removable bottom) with about a tablespoon of softened butter. Grab the pastry dough out of the food processor bowl and use your hands to quickly shape the dough into a compact ball. Transfer the dough to your greased tart pan and use your fingers to press the dough flat against the bottom and sides of the tart pan. Alternatively, you can roll the tart dough out a bit first using a rolling pin, then transfer the dough to your pan and use your fingers to finish molding the dough inside the tart pan.

Step 3

Grab a rolling pin and slide it across the top of the tart pan to trim off excess dough from the top edges of the pan. Use a fork to prick the dough all over the bottom of the pan. Place the tart pan in the freezer to chill for 30 minutes.

Step 4

Preheat the oven to 400°F. Once the oven is ready, place a sheet of parchment paper on the inside of the tart pan and pour dried beans or pie weights into the parchment paper. Blind-bake the pastry dough for 12 minutes. Remove the parchment paper and weights, then continue baking for another 12 minutes, until the dough is slightly golden and baked throughout.

Step 5

Remove the tart shell from the oven and allow it to rest on the counter while you prepare the lemon filling. Lower the oven heat to 350°F.

Step 6

Add all of the lemon filling ingredients to a medium saucepan. Whisk over low heat until the butter is melted and the mixture is completely smooth.

Step 7

Continue cooking the lemon filling over medium-low heat (closer to the low end than the medium end), patiently whisking the entire time. Cook until the lemon filling has completely thickened and has a pudding like consistency. This can take up to 20 minutes. When you give the filling a stir with a wooden spoon, it should easily coat the spoon and clearly mound up when it falls off the spoon back into the saucepan. --- Please see notes.

Step 8

Pour the lemon filling into your prepared tart pan. Bake the tart for approximately 20 minutes. The edges of the lemon tart should be set and the center should have a wobble.

Step 9

Remove the tart from the oven and let it rest in the pan until room temperature. Place the lemon tart on top of a wide-rimmed cup, removing the fluted edge from the tart. Set the tart in the fridge to chill, then dust with powdered sugar before serving.