Temper the crust: Take 1 refrigerated rolled pie crust (about 11 inches) out of the fridge and leave it sealed on the counter. Cold dough cracks along the fold lines when you unroll it; 15 minutes fixes that. Line a rimmed sheet pan with parchment.

Preheat with a hot surface: Set a rack in the lower third with a second sheet pan or baking steel on it, and heat the oven to 400°F (205°C). Baking on a preheated surface is what keeps the bottom from going soggy under the berry juice.

Toss the fruit: In a bowl, combine 170 grams raspberries, 140 grams blueberries, 65 grams granulated sugar, 2 tablespoons cornstarch, the zest and juice from 1 medium lemon (zest plus 2 tsp juice), and 1 pinch kosher salt. Fold gently so the raspberries stay whole. Do this right before assembly — the longer it sits, the more juice you have to manage.

Assemble: Unroll 1 refrigerated rolled pie crust (about 11 inches) onto the parchment. Scatter 2 tablespoons almond flour (or fine dry breadcrumbs) over the center, leaving a 2-inch border bare; it absorbs juice as the fruit cooks. Mound the fruit over the almond flour, dot with 15 grams cold unsalted butter, cut into small bits, then fold the border up over the edge of the fruit in overlapping pleats. Press each pleat where it overlaps so it does not unfold in the oven.

Wash and sugar: Brush the pleated border with 1 large egg, beaten and sprinkle on 1 tablespoons turbinado or demerara sugar. Slide the whole parchment onto the preheated pan.

Bake: Bake until the crust is deep golden and the juices bubble thickly at the center rather than running thin. Start checking at 35 minutes. If the edge browns well ahead of the fruit, tent it loosely with foil.

Cool before cutting: Slide the parchment onto a rack. The cornstarch sets as it cools; cutting hot gives you a puddle. Serve warm or at room temperature.