Blackberry-Almond Shortbread Squares

« » Preheat oven to 350 degrees. Butter a 9-by-13-inch baking pan. Line with parchment; butter lining. Dust with flour; tap out excess. Arrange nuts in a single layer on a rimmed baking sheet. Bake until golden, 15 minutes; let cool. Grind in a food processor until fine.

Whisk together flour, nuts, salt, and cinnamon in a medium bowl; set aside. Put 3/4 cup plus 1 tablespoon sugar and the butter in the bowl of an electric mixer fitted with the paddle attachment; mix until pale and fluffy, about 3 minutes. Mix in almond extract. Add flour mixture in 2 batches; mix until a crumbly dough forms.

Press all but 1 cup dough onto bottom of pan. Toss berries with zest; scatter over dough. Sprinkle with remaining tablespoon sugar; crumble reserved dough on top. Bake until golden, about 30 minutes. Let cool on a wire rack. Cut into 12 squares; dust with sugar.