Roll out 375g of sweet shortcrust pastry and line a 9in / 23cm tart ring set on a baking sheet, then chill it. Preheat the oven to 400°F / 200°C.
Prick the base, line with parchment paper and baking beans, and bake for 15 minutes. Remove the paper and beans and bake for 5-10 minutes, until crisp and golden. Reduce the oven to 300°F / 150°C.
Zest 3 unwaxed lemons and juice them with 2 more lemons. Whisk 6 eggs with 250g of superfine sugar. Stir in 200ml of heavy cream, the zest, and the juice, then strain.
Pull the oven rack halfway out and pour the filling into the case. Bake for 35-40 minutes, until barely set. Cool, trim the pastry edges, and chill.
