# What You'll Need:
→ Shortbread crust
01 - 1 cup (2 sticks) unsalted butter, softened
02 - 1/2 cup granulated sugar
03 - 2 cups all-purpose flour
04 - 1/2 teaspoon fine salt
→ Blackberry swirl
05 - 1 cup fresh or frozen blackberries
06 - 2 tablespoons granulated sugar
07 - 1 teaspoon fresh lemon juice
→ Lemon filling
08 - 1 1/2 cups granulated sugar
09 - 1/4 cup all-purpose flour
10 - 4 large eggs
11 - 2/3 cup freshly squeezed lemon juice (about 3–4 lemons)
12 - Zest of 2 lemons
# Directions:
01 - Preheat oven to 350°F. Line a 9x9-inch baking pan with parchment paper, leaving a 1-inch overhang for easy removal; set the pan aside.
02 - In a medium bowl, beat the softened butter and granulated sugar until light and fluffy. Add the flour and salt and mix just until the dough comes together, avoiding overworking.
03 - Press the dough evenly into the prepared pan using your fingers or an offset spatula to form a compact layer. Bake at 350°F for 18–20 minutes, or until the edges are set and the surface is a pale golden; remove from oven and set aside while preparing the fillings.
04 - Combine blackberries, sugar and lemon juice in a small saucepan over medium heat. Cook, mashing the berries with the back of a spoon, until the mixture thickens, about 4–6 minutes. Press through a fine-mesh sieve to remove seeds and reserve the smooth puree; allow to cool slightly.
05 - In a large bowl, whisk together the granulated sugar and flour. Add the eggs, lemon juice and lemon zest and whisk until fully combined and smooth.
06 - Pour the lemon filling evenly over the warm pre-baked crust. Drop small spoonfuls of the blackberry puree across the filling and use a skewer or knife to gently swirl the puree into a marbled pattern.
07 - Return the pan to the oven and bake at 350°F for 20–22 minutes, until the center is just set and the surface appears slightly matte. Remove from the oven and cool on a wire rack.
08 - Cool completely in the pan, then refrigerate for at least 2 hours to firm. Use the parchment overhang to lift the slab from the pan and slice into 16 bars. Dust with powdered sugar if desired and store refrigerated in an airtight container for up to 4 days.