A recipe that dates back to the Middle Ages, yet is still found throughout Tuscany even today. The ground almond-spinach filling is light and satisfyingly spongy -- almost soufflé-like. As with zucchini bread and carrot cake, the spinach contributes an earthy undertone, moistness, and an unusually brilliant color. -From Dolci: Italy's Sweets
For the crust: In a large bowl, in a food processor, or on a clean work surface, mix the flour, butter, and sugar until the mixture resembles coarse sand.
Add the egg yolks, baking powder, zest and salt and mix until dough forms.
Roll the dough into a disc, cover with plastic wrap, and refrigerate for at least 30 minutes before rolling out.
Lightly butter a 10-inch deep-dish pie pan. Roll out 2/3 of the dough, making it large enough to hang well over the sides. If you like, make a series of “fret” shapes along the outer edge of the dough. To do that, fold the edges of dough over, and cut into the edges and gently press “fret” shapes by pinching the dough between thumb and forefinger at a distance of about 1/2 inch apart.
Using a fork poke holes throughout the entire bottom and sides of the Roll out the remaining dough to form lattices over the top of the filling. Refrigerate all the dough, covered in plastic wrap, until ready to use.
For the filling: Cook the spinach in a few ounces of salted water until tender. Allow to cool. Squeeze out all the cooking liquids, and finely chop in a mini food processor. Reserve.
In food processor, grind the almonds until they resemble coarse sand. Reserve.
In a bowl, beat the yolks with 1/3 cup of the sugar until creamy and light yellow. Add the almonds and beat until well combined. Add the spinach, candied peel, and liqueur and mix until well combined.
In a separate bowl, beat the whites until soft peaks form, then add in the remaining 1/3 cup of sugar and beat until it forms a glossy meringue.
Slowly fold the meringue into the yolk mixture. Pour into the prepared pie crust. Sprinkle with the pine nuts and top with the remaining dough in a lattice pattern.
Bake for about 1 hour, until golden. Allow to cool to room temperature, then serve sprinkled with confectioners’ sugar.