How to Make It
In a medium bowl, combine the flour and cubed butter. Using your fingertips, rub the butter into the flour until the mixture resembles fine breadcrumbs. Stir in 1/2 cup of the sugar, the lemon zest and salt. In a small bowl, beat 2 of the eggs; add to the flour mixture and stir with a wooden spoon until a dough starts to come together. Knead with your hands just until a dough forms. Divide the dough into a one-third piece and a two-thirds piece; pat each piece into a 1-inch-thick disk and wrap in plastic. Refrigerate for at least 1 hour or overnight.
Preheat the oven to 350°. Lightly butter a 9-inch fluted tart pan. In a small bowl, whisk the ricotta with 1 egg, the egg yolk and the remaining 1/4 cup of sugar until blended.
On a lightly floured surface, using a lightly floured rolling pin, roll out the larger piece of dough to a 12-inch round about 1/8 inch thick. Ease the dough into the prepared tart pan and trim off the excess; prick the bottom of the dough all over with a fork. Spread the jam in an even layer over the bottom of the tart and spread the ricotta mixture evenly on top of the jam.
Roll out the remaining piece of dough to a 10-inch round. Using a sharp knife, cut the pastry into strips of different widths and arrange on top of the ricotta, leaving space between the strips and pressing them to adhere to the rim of the pan.
In a small bowl, beat the remaining egg and brush onto the pastry strips. Bake the tart in the center of the oven for about 50 minutes, until the crust is golden and the filling is set. Transfer to a rack and let cool to room temperature. Cover and refrigerate overnight. Serve chilled, with whipped cream.