1. Prepare the crust: Whisk egg yolk and heavy cream in a small bowl; set aside. In a large bowl, combine flour, salt, and sugar. Add cold butter, working it into the dry ingredients until crumbly. Gradually add the egg mixture, mixing until dough forms. Wrap and chill for about one hour.
2. Roll out chilled dough to fit a 9 or 10-inch tart pan with a removable base. Press evenly, dock with a fork, trim edges, and freeze for 30 minutes.
3. Preheat oven to 375°F (190°C). Blind bake crust for 20 minutes until golden. Reduce oven to 350°F (175°C), cool completely before filling.
4. For lemon curd: Whisk eggs and yolks. In a saucepan, combine zest, lemon juice, sugar, and butter, stirring until butter melts. Remove from heat, drizzle in eggs while whisking. Return to low heat, stir until thickened.
5. Strain curd through a sieve, cover with plastic wrap. Pour into cooled shell, spread evenly. Bake 10 minutes at 350°F (175°C), then chill for 2-4 hours.