If you don’t have a double boiler, you can easily create one by resting a stainless-steel bowl on top of a saucepan partially filled with simmering water. Make sure the bottom of the bowl does not touch the water.
- 1 tart dough disk, at cool room temperature
- 1 Tbs. cornstarch
- 2 Tbs. water
- 5 eggs
- 2 tsp. finely grated lemon zest
- 2/3 cup fresh lemon juice
- 3/4 cup sugar
- 6 Tbs. (3/4 stick) unsalted butter, cut into small pieces
- Whipped cream for serving (optional)
Bake the tart shell
Preheat an oven to 425°F.
On a lightly floured surface, roll out the dough disk into a 10 1/2-inch round. Gently transfer the dough to a 9 1/2-inch tart pan with a removable bottom. Fold the overhang back over itself and press it into the sides of the pan to make a sturdy rim. Freeze for 5 minutes.
Bake the tart shell until golden brown, 15 to 18 minutes. Transfer to a wire rack and let cool.
Prepare the filling
In a small bowl, dissolve the cornstarch in the water. In the top pan of a double boiler, whisk together the eggs, lemon zest, lemon juice, sugar and cornstarch mixture. Place over simmering water in the bottom pan and whisk until thickened, about 10 minutes. Remove from the heat and whisk in the butter.
Finish the tart
Pour the warm filling into the baked tart shell. Refrigerate for at least 2 hours or up to 24 hours. Remove the pan rim and cut the tart into wedges. Top each serving with a dollop of whipped cream and serve. Makes one 9 1/2-inch tart.
Adapted from Williams-Sonoma Food Made Fast Series, Baking, by Lou Seibert Pappas (Oxmoor House, 2006).