Step 1: Make the Raspberry Puree
Add raspberries to a blender or food processor and blend until smooth. Pour the puree through a metal sieve to remove the seeds.

Transfer the seedless puree to a saucepan. Simmer over medium heat until it reduces to about ¼ to ⅓ cup. This will take 15–20 minutes.

Let the puree cool completely while you prepare the base and filling. Cooling is important so it doesn’t scramble the eggs in the custard.

Step 2: Prepare the Shortbread Base
Preheat your oven to 325°F (160°C). Line a 9×13-inch pan with parchment paper, leaving extra hanging over the sides.

In a bowl, whisk together flour, sugar, cornstarch, and salt. Stir in the melted butter until the dough is thick and crumbly.

Press the mixture evenly into the prepared pan, creating a slight edge around the perimeter. This helps contain the filling later.

Bake for 20–25 minutes, until set and lightly golden. Remove from the oven and gently prick the top with a fork—just the surface, not all the way down.

Step 3: Prepare the Lemon Raspberry Layer
While the crust bakes, whisk together sugar and cornstarch in a large bowl. This helps eliminate any lumps before the wet ingredients go in.

Add the eggs and whisk until smooth. Then add the cooled raspberry puree and lemon juice, mixing until fully combined.

The mixture will be quite liquid, but don’t worry—it will set as it bakes. Avoid overwhisking to keep the custard from becoming foamy.

Step 4: Bake the Bars
Pour the lemon raspberry mixture over the warm shortbread crust. Tilt the pan gently to distribute it evenly.

Return to the oven and bake at 325°F (160°C) for another 20–25 minutes. The top should look set, not jiggly, and just slightly glossy.

Cool the bars at room temperature for at least 1 hour. Then chill them in the fridge for 2–3 hours to help them firm up completely.

Step 5: Slice and Serve
Once fully chilled, use the parchment paper to lift the bars out of the pan. Transfer to a cutting board.

Slice with a sharp knife, wiping it clean between each cut for neat, even bars. Dust with powdered sugar just before serving if desired.

Store leftovers in an airtight container in the fridge for up to 4 days. They hold their shape and flavor beautifully.