Recipe from Cooks Illustrated
• 1 fully baked warm tart shell (9- to 9 1/2-inch)
• 7 large egg yolks
• 2 large eggs
• 1 cup granulated sugar
• 2 tablespoons granulated sugar
• 2/3 cup lemon juice from 4 to 5 medium lemons
• 1/4 cup grated lemon zest
• pinch table salt
• 4 tablespoons unsalted butter, cut into 4 pieces
• 3 tablespoons heavy cream
Adjust oven rack to upper-middle position and heat oven to 375 degrees. Place tart pan with shell on cookie sheet.
In medium non-reactive bowl, whisk together yolks and whole eggs until combined, about 5 seconds. Add sugar and whisk until just combined, about 5 seconds.
Add lemon juice, zest, and salt; whisk until combined, about 5 seconds.
Transfer mixture to medium non-reactive saucepan, add butter pieces, and cook over medium-low heat, stirring constantly with wooden spoon, until curd thickens to thin sauce-like consistency and registers 170 degrees on an instant-read thermometer, about 5 minutes.
Immediately pour curd through single-mesh stainless steel strainer set over clean non-reactive bowl. Stir in heavy cream; pour curd into warm tart shell immediately.
Bake until filling is shiny and opaque and until the center 3 inches jiggle slightly when shaken, 10 to 15 minutes. Cool on wire rack to room temperature, about 45 minutes. Remove outer metal ring, slide thin metal spatula between bottom crust and tart pan bottom to release, then slip tart onto cardboard round or serving plate. Cut into wedges and serve.