Raspberry Puree:

The first step to creating these Lemon Raspberry Bars is preparing the raspberry puree. Begin by adding the fresh or frozen raspberries into a blender or food processor. Pulse them until smooth. To ensure a velvety texture, pour the raspberry puree into a metal sifter and push it through to remove the seeds. This step is optional but highly recommended for an extra-smooth custard layer.

Once the puree is free of seeds, transfer it to a small saucepan and place it over low-medium heat. Allow the puree to gently boil, stirring occasionally. This process helps thicken the puree by removing excess liquid. You’ll need to cook it for approximately 15-20 minutes until the puree reduces down to about ¼ to ⅓ cup. After it reaches the desired consistency, remove it from the heat and let it cool.

Shortbread Base:

Now it’s time to prepare the shortbread crust. Preheat the oven to 325°F (160°C) and line a 9×13 inch baking pan with parchment paper, ensuring there’s enough overhang on the sides for easy removal after baking.

In a medium bowl, whisk together the flour, granulated sugar, cornstarch, and salt. Stir in the melted butter until the mixture is thick and well-combined. This will form the dough for your shortbread crust. Press the dough firmly into the bottom of the prepared pan, making sure to create a slight lip around the edge. Bake the crust in the preheated oven for 20-25 minutes or until the top is set and slightly golden. Once baked, remove from the oven and gently prick the top of the crust with a fork, making sure not to poke all the way through. This will prevent the crust from puffing up during the next steps.

Lemon Raspberry Layer:

While the shortbread base is baking, prepare the lemon raspberry custard layer. In a large bowl, whisk together the granulated sugar and cornstarch, ensuring there are no lumps. Add in the six large eggs and whisk until the mixture is smooth. Carefully whisk in the cooled reduced raspberry puree, followed by the freshly squeezed lemon juice. The mixture will be liquid at this stage, but that’s perfectly fine. Once the custard is fully mixed, pour it evenly over the baked shortbread crust.

Return the pan to the oven and bake for an additional 20-25 minutes at 325°F (160°C) until the top of the custard layer looks set. The center may still slightly jiggle, but it will firm up as it cools. Remove from the oven and allow the bars to cool to room temperature for about an hour. Once cooled, cover the pan and place it in the refrigerator to chill for at least 2 hours. This chilling time helps the bars set and makes slicing easier.

Serving and Slicing:

When ready to serve, carefully lift the bars out of the pan using the overhanging parchment paper. Place the bars on a cutting board and use a sharp knife to slice them into squares. For clean cuts, wipe the knife between each slice. These bars can be stored in an airtight container in the refrigerator for up to 5 days.