2 sticks + 5 T unsalted butter, cut into T size, room temperature
Put flour, sugar, and salt in processor and pulse to combine. Add butter and pulse until mixture has pieces the size of peas and smaller. Break up the yolk and add a little at a time, pulsing after each addition. After the egg is added, pulse for 10 seconds at a time until the dough forms clumps. Then, turn the dough out onto a surface and very lightly knead the dough just to incorporate any dry ingredients.
Butter a 9-inch tart pan with a removable bottom and press the dough evenly into the bottom and up the sides, saving a bit of leftover dough for any patching of cracks that may occur during baking (optional). Freeze the dough for at least 30 minutes before baking (can be longer). Center a rack in the oven and preheat to 375F. Butter the shiny side of a piece of aluminum foil and place the buttered side tightly against the dough. Put the tart pan on a baking sheet and bake for 25 minutes. Carefully remove the foil. If the crust has puffed, press down those areas with the back of a spoon. Bake for another 8 minutes or until crust is firm and golden brown. Transfer to cooling rack and allow to come to room temperature.
Bring a few inches of water to a simmer in a saucepan. In a large heatproof bowl (off the heat, at this point), combine sugar and zest between your fingers until grainy. Whisk in eggs, then lemon juice. Set bowl over pan and whisk once the mixture becomes tepid. Cook mixture until it becomes 180F. You must whisk continuously to prevent the eggs from scrambling. The mixture will become foamy, then thicken as it gets closer to 180F - and be warned, it takes at least 10 minutes.
When it reaches 180F, strain the cream into the blender and discard the zest. Let the cream cool, stirring occasionally, to 140F, about 10 minutes. Turn blender to high and add butter, 5 pieces at a time, scraping down sides as needed. Once all the butter is in, blend for 3 more minutes. Pour the cream into a container and place a piece of plastic wrap on the surface of the cream; refrigerate for at least 4 hours. Then, loosen cream with a whisk and spoon into tart shell. Serve immediately or refrigerate. ENJOY!