Whisk the egg yolk and cream together in a small bowl and set aside.

In a large bowl, whisk together the flour, sugar, and salt. Add the cubed butter. Work the butter in with a pastry cutter or your clean hands. Once you have a crumbly mixture with roughly pea-sized pieces of butter throughout you can drizzle in the yolk cream mixture. Mix together with a fork or knife.

Knead the dough together in the bowl a few times, just to bring it together into one ball. Then shape the dough into a disk, wrap tightly in plastic wrap, and chill for about an hour.

Lightly flour your surface and roll the dough into a circle then transfer to a 9-inch tart pan (one with a removable base is preferable). Press the dough into the pan and up the sides, and trim any excess flush with the top edge of the pan. Pierce the crust all over the bottom with the times of a fork. Freeze for about 30 minutes.

While the crust is freezing, preheat your oven to 375°F.

Place the frozen crust on a baking sheet, and bake for about 20 minutes or until a light golden color. Remove the crust from the oven and reduce the oven temperature to 350°F.

In a medium pot, combine the sugar, butter, lemon zest and juice and place over medium heat. Stir often until the butter is melted and the mixture just starts bubbling, then remove from heat. Slowly drizzle the hot butter mixture into the egg mixture while whisking vigorously.

Pour the egg mixture back into the pot and place it over low heat, gently whisking constantly, until the mixture thickens and just starts to bubble, about 170F. (Your curd is done once it coats the back of a wooden spoon; you can swipe a finger across and a track will be left in the curd.)

Strain the curd through the sieve into the bowl to remove any potential clumps of cooked egg. Then, pour the curd into your tart shell and smooth the surface. Bake for 10 minutes or until the edge is just set. Let the tart cool for an hour at room temperature, then refrigerate it for 2 hours before serving.