How to Make It
In a food processor, combine the flour, sugar and a pinch of salt and pulse to blend. Add the butter and pulse until the mixture resembles coarse meal. Transfer the mixture to a bowl. Add the egg and stir with a fork until the pastry just comes together. Transfer the pastry to a lightly floured work surface and knead a few times. Pat the pastry into a disk, wrap in plastic and refrigerate for at least 1 hour.
On a lightly floured surface, roll out the pastry to a 13-inch round. Ease the pastry into an 11-inch tart pan with a removable bottom, pressing it into the corners and up the sides without stretching. Trim any overhang and prick the bottom with a fork. Refrigerate until chilled, at least 20 minutes.
Preheat the oven to 350°. Line the pastry with foil and fill with pie weights or dried beans. Bake the shell on the bottom shelf of the oven for 10 minutes, or until it starts to dry out. Remove the foil and weights and bake the shell for 10 minutes longer, or until it begins to brown around the edge. Transfer to a wire rack to cool; leave the oven on.
In a large bowl, mix the ricotta with the sugar and cornstarch. Stir in the lemon zest, vanilla and eggs. Scrape the filling into the pastry shell and smooth the top. Bake on the bottom shelf of the oven for about 20 minutes, or until the filling is just set. Cool the ricotta tart on a wire rack before unmolding. Serve warm or at room temperature.