Combine flour, powdered sugar, and salt in a bowl
Add cold butter and rub together with fingertips until the mixture resembles coarse sand
Add egg yolk and 1 tbsp cold water and mix until dough just comes together
Flatten into a disc, wrap in plastic, and refrigerate for 30 minutes
Roll dough out on a lightly floured surface to 3mm thickness
Press into a 9-inch tart pan, trim edges, and prick the base with a fork
Freeze for 15 minutes, then blind bake at 180°C (350°F) for 15 minutes with weights
Remove weights and bake a further 8–10 minutes until deep golden and dry
Cool completely on a wire rack before filling
Whisk egg yolks, lemon juice, lemon zest, and sugar together in a small saucepan
Cook over medium-low heat, stirring constantly, until thickened — about 8–10 minutes
Remove from heat, add butter cubes, and stir until fully melted and glossy
Press plastic wrap directly onto the surface and refrigerate
