Here are the ingredients for both the crust and filling:
2 sticks (16 tablespoons) unsalted butter
1/2 teaspoon vanilla extract
1/4 cup confectioners' sugar
1 pinch salt
1 1/4 cup unbleached all-purpose flour
2 large eggs at room temperature
3 large egg yolks at room temperature
1 cup regular (granulated) sugar
1/2 cup freshly squeezed lemon or lime juice (about 4 lemons or 5 limes)
Pie pan with flat removable bottom (optional, but very handy for cutting and serving without breaking the crust)
Step 1: Pie Crust
Melt one stick (8 tablespoons) unsalted butter and let cool
Combine melted butter, 1/2 tsp vanilla extract, 1/4 cup confectioners' sugar and pinch of salt and blend with a spoon.
Gradually add flour till you form a smooth, soft dough with a consistency similar to cookie dough
Place in center of pan and press down with fingertips as evenly as possible on bottom and sides of the pan
Bake in the center of the oven for 12 to 15 minutes, till it's lightly browned. You do not need to prick or weigh this crust.
Step 2: Pie Fill
Cut one stick of butter into 8 pieces.
Combine eggs, egg yolks and sugar in double boiler.
Place over simmering water. The top pan should be just above, not touching the simmering (not boiling) water.
Whisk, and watch the mixture transform. It will start bright yellow and grainy. As the sugar melts it become more liquid, paler, and frothy on top. After about 8 to 10 minutes it will thicken and become pale lemon colored.
Add butter, one piece at a time, letting each piece melt before adding the next.
Add the lemon or lime juice. When I use lime I also put in a bit of green food coloring, just so people eating the pie will know what flavor to expect. Continue whisking until the mixture is thick and custard-like and the first bubbles appear -- but do not let it boil. This will take about 3 or 4 minutes.
Step 3: Finish!
Leave it to set for a minimum of 30 minutes. Although you can put it in the refrigerator (it will help it set) serve the tart at room temperature.