For the Dough: place flour, almond meal, sugar and sea salt into the bowl of a food processor and process to mix. Add butter and process until mixture resembles coarse crumbs. With top part of food processor cover removed, add 3 tablespoons ice-cold water while processing and continue until a dough forms. Turn dough out onto a lightly floured surface. Knead until dough is smooth. Shape into a 20- cm disk. Wrap in plastic wrap and refrigerate for 1 hour.
Preheat oven to 220°C (200°C fan forced). For the filling, reserve 1 tablespoon of sugar for use later, mix remaining sugar, flour, cinnamon and sea salt in a large bowl. Add pears, barberries and almond extract; toss gently to coat. Set aside.
Roll dough between 2 pieces of baking paper into a disk (30-cm diameter). Place dough onto a baking paper-lined baking tray. Spoon filling into centre of dough, spreading to within 4-cm of edge. Fold edge of crust up over fruit, leaving the centre filling exposed, pleating or folding crust as needed. Brush crust with beaten egg and sprinkle with sliced almonds and reserved tablespoon of sugar.
Bake the crostata on the middle rack of the oven for 25 to 30 minutes or until pears are tender and crust is golden brown. Cool slightly on baking tray. Cool completely on wire rack. Serve with ice cream or whipped cream, if desired.
Bosc pears can be substituted with green apples or firm nectarines depending on availability and the season.