1. Preparation
Preheat the oven to 350°F (175°C).
Gather all ingredients and equipment: a tart pan, mixing bowls, whisk, and saucepan.
Zest and juice the lemons, setting aside 1 cup of lemon juice and 2 tablespoons of zest.
In a mixing bowl, combine 1 1/4 cups all-purpose flour with 1/2 cup powdered sugar and a pinch of salt.
2. Making the Crust
Add 1/2 cup cold unsalted butter, cubed, to the flour mixture.
Using a pastry cutter or your fingers, blend the butter into the dry ingredients until the mixture resembles coarse crumbs.
Pour in 1 large egg yolk and 2 tablespoons cold water, mixing until the dough forms.
Press the dough into the bottom and up the sides of a tart pan, then refrigerate for 10 minutes.
Blind bake the crust for 15-20 minutes until golden. Remove from oven and let it cool.
3. Making the Lemon Curd
In a saucepan over medium heat, whisk together 1 cup granulated sugar, 1/4 cup unsalted butter, and 1 cup lemon juice.
Once melted, slowly whisk in 4 large eggs and lemon zest until fully combined.
Continue cooking over medium heat, stirring constantly, until the mixture thickens and coats the back of a spoon, about 10 minutes.
Remove from heat and strain the curd through a fine mesh sieve to remove any lumps.
4. Assembling the Tart
Pour the lemon curd into the cooled tart shell, spreading it evenly.
Bake the tart for an additional 10-15 minutes until the curd is set.
Remove from oven and let it cool at room temperature before refrigerating for at least 1 hour.
5. Serving
Once chilled, remove the tart from the tart pan.
Dust with powdered sugar before serving.
Garnish with lemon slices or berries if desired.