Preheat the oven to 375 degrees F.

In a medium-size bowl, mix together the flour, melted butter, confectioners’ sugar, and salt until it forms a soft dough. Then press it into the base of the tart shell and up the sides. Dock the dough with a fork so that it bakes evenly.

Cover the unbaked crust with parchment paper or aluminum foil tightly against the crust, covering the edges to prevent them from over-browning. Fill the surface with pie weights, dried beans, or uncooked rice.

Bake the crust for 20 minutes, I like to use nonstick foil. Carefully remove the weights and foil, return to the oven and bake for another 5 to 8 minutes, or until the crust is golden and dry. Remove from the oven and let cool completely.

Fill a saucepan with 1 to 2 inches of water. Place on high heat and once the water comes to a boil, reduce to low heat and keep the water simmering.

In a heatproof glass bowl that fits on top of the saucepan, whisk together the eggs, granulated sugar, lemon zest, lemon juice, and heavy cream until well blended. Be sure that the water does not touch the bottom of the bowl.

Whisk constantly as the curd cooks for about 10 minutes, or until the mixture thickens. This can take anywhere from 10 to 20 minutes. (For me, it takes about 11 minutes). Lemon curd thickens at 170 degrees on an instant-read thermometer.

Once thickened, remove the curd from the heat and immediately strain through a fine-mesh sieve. Add the butter, a few cubes at a time, whisking until the butter is melted, completely combined and the curd is smooth. The lemon curd will continue to thicken as it cools. Take your time whisking the butter into the lemon mixture as it will add a lighter texture to the tart.

Let the curd cool to room temperature before filling the tart shell. Using an offset spatula, spread the curd evenly. Refrigerate for at least 4 hours. Serve with fresh fruit or sweetened whipped cream.