This is a classic French style of lemon tart topped with fresh strawberries. It can also be made to fit into a rectangular tart pan. Simply cut all proportions in half (all cook and bake times remain the same).
2/3 cup (150 grams) unsalted butter, cut into pieces
1/2 cup (125 milliliters) full fat sour cream
1.9 liters fresh strawberries, hulled and halved or sliced
Apple jelly, for glazing (optional)
Beat the butter and icing sugar together until smooth.
Push the hard boiled egg yolk through a sieve and stir the raw egg yolk and vanilla into it. Add this to the butter mixture and stir until blended.
Add the flour and salt to the butter mixture and stir until blended. Shape the dough into a disc (it will be very soft), wrap in plastic and chill until firm, about two hours.
On a lightly floured work surface, gently knead the dough just a little soften, then roll it out to a circle about 30 centimeters across and six millimeters thick. Carefully lift this and line a 22 centimeter removable-bottom fluted tart pan, press it into the bottom and sides and trim away any excess dough. Chill the tart shell for 30 minutes.
Preheat the oven to 325 °F (160 °C). Place the chilled tart shell onto a baking tray and dock the bottom of the pastry with a fork. Bake the tart shell for about 20 minutes, until the edges just begin to brown. Cool the tart shell to room temperature.
For the filling, whisk the eggs, egg yolks, sugar, lemon zest and lemon juice together in a metal bowl and place this over a pot of gently simmering water. After a minute, add the butter and continue to whisk until the curd has thickened, about five minutes. Remove the curd from the heat, strain and whisk in the sour cream. Pour the warm curd into the cooled tart shell and chill, uncovered, until set, about two hours. Arrange the strawberries on top of the tart close to when you plan on serving. If you wish to assemble more than an hour ahead, melt the apple jelly and glaze the fruit with it, using a pastry brush.