Preparation

Make the peach preserves

• Put the peaches, brown sugar, and lemon juice in a medium heavy-duty saucepan. Cook over low heat to dissolve the sugar, about 10 minutes. Raise the heat to medium and bring to a boil. Cook, stirring often, until the peaches are tender and the liquid is thickened and syrupy, about 10 minutes. Stir in the cinnamon and nutmeg, and simmer until thickened to a jam consistency, 5 to 10 minutes more. You should be able to drag a path through the bottom of the saucepan with a silicone spatula. Scrape the peaches into a heatproof bowl and let cool completely. (The preserves can be stored in an airtight container in the refrigerator for up to 2 weeks.)

Make the frangipane

• Put the almond flour, sugar, butter, egg, almond and vanilla extracts, and salt into a food processor fitted with the metal blade. Pulse until the mixture is combined, scraping down the bowl as necessary. Scrape into a bowl, cover, and refrigerate for up to 1 hour.

Make and assemble the tart

• Position a rack in the center of the oven, put a large rimmed baking sheet on the rack, and heat the oven to 350°F. Remove the pasta frolla from the refrigerator and let it rest at room temperature for 30 minutes. Have ready a 9-inch fluted tart pan with a removable bottom.
• Lightly dust a work surface and rolling pin with flour. Roll the larger disk of pasta frolla into a 12-inch circle, lifting and turning the dough as you roll to prevent sticking and create an even round. Gently wrap the dough around the rolling pin and unroll it
  over the tart pan. Gently fit the dough into the pan without stretching it. Use the palm of your hand or the rolling pin to trim off
  the excess. Refrigerate while you roll out the second piece of dough.
• Roll the smaller piece into a 10-inch circle, and use a fluted pastry wheel to cut it into strips from 1/2 inch to 1 inch wide. Remove the crostata base from the refrigerator. Spread the frangipane evenly over the crostata base. Spoon the cooled peach preserves over the frangipane in an even layer. If the preserves are syrupy, use a slotted spoon to separate the peaches and syrup, and reserve the leftover syrup for another use (it’s delicious spooned over yogurt or vanilla ice cream). Position the strips of pastry on top of the peaches in a crisscross lattice pattern. You can weave the strips if you like, but the dough is fragile and tends to tear so it’s not necessary (nor is it traditional). Press the edges of the strips into the edge of the tart shell to secure and trim off the excess.
• Set the crostata on the heated baking sheet, and bake until the crust is golden-brown, about 40 minutes. Transfer from the baking sheet to a rack to cool completely. Remove the ring and use a large, wide-angled spatula to transfer the crostata from the metal tart base to a serving plate.