Start by preheating your oven to 350°F (175°C). Grease an 8x8 inch baking pan or line it with parchment paper to ensure easy removal of the bars later.
In a medium bowl, mix together the all-purpose flour, powdered sugar, and salt. Add the softened butter to the bowl and use a fork or pastry cutter to blend these ingredients until the mixture resembles coarse crumbs.
Take the crumbly mixture and evenly press it into the bottom of your prepared baking pan to form a solid base for the bars. Place it in the oven and bake for about 15 minutes, or until the crust is lightly golden.
While the crust is baking, prepare the lemon filling. In another bowl, whisk together the eggs, granulated sugar, lemon zest, and fresh lemon juice until the mixture is smooth and well combined.
In a small separate bowl, gently toss the fresh raspberries with the cornstarch and the additional 2 tablespoons of granulated sugar. This step helps to thicken the raspberries and adds sweetness.
After the crust has finished baking, carefully pour the lemon mixture over the baked crust, smoothing it out with a spatula if necessary. Evenly scatter the sweetened raspberries on top of the lemon filling.
Return the pan to the oven and bake for an additional 25-30 minutes. The edges should be set, and the center should feel slightly firm to the touch when done.
Once baked, remove the pan from the oven and allow it to cool completely in the pan before lifting it out using the parchment paper. Cut into bars and, if desired, dust with powdered sugar for a lovely finish before serving.
Notes
Serve chilled or at room temperature, garnished with fresh raspberries or mint.