📖 Instructions

1. Before you begin, get your oven ready! Preheat it to 350°F (175°C). Then, line a 9x13 inch baking pan with parchment paper, leaving an overhang on the longer sides. This little trick is super helpful for lifting the finished bars out easily. Give the parchment a light spray with non-stick cooking spray, just to be extra sure nothing sticks.
2. First up, the shortbread crust. In a large mixing bowl, combine the all-purpose flour, granulated sugar, and a pinch of salt. Make sure it's all mixed together really well – no lumps allowed! Now, take your very cold unsalted butter (it's essential it's cold for that perfect crumbly texture!) and cut it into small cubes. Add these cubes to the dry ingredients.
3. Using a pastry blender, a fork, or even your clean fingertips, 'cut' the butter into the flour mixture. You want to work quickly here so the butter doesn't get too warm. Keep going until the mixture resembles coarse crumbs, kinda like wet sand. Don't overmix; small pieces of butter are good!
4. Press this crumbly mixture firmly and evenly into the bottom of your prepared 9x13 inch baking pan. You can use the bottom of a flat-bottomed glass or your hands to really compact it. This creates a sturdy base for your bars. Once pressed, poke holes all over the crust with a fork; this prevents it from puffing up too much.
5. Pop the pan into your preheated oven and bake the crust for 20-22 minutes, or until the edges are lightly golden. While it's baking, you can start on the lemon-raspberry filling. Once baked, remove the crust from the oven but leave the oven on.
6. Now for the glorious filling! In a separate large mixing bowl, whisk together the large eggs until they're nicely beaten. Add the granulated sugar and continue to whisk vigorously until the mixture is light in color and fluffy, about 1-2 minutes. This incorporates air and helps with the texture.
7. Next, whisk in the all-purpose flour until there are no lumps remaining. It should be a smooth, slightly thick batter. Don't worry if it seems a bit heavy at this stage, we're adding liquids next!
8. Carefully add the fresh lemon juice and the lemon zest to the egg mixture. Whisk everything together until it's perfectly combined. You'll notice the mixture thins out a bit, and you'll get that amazing fresh lemon smell! It’s truly invigorating.
9. Gently fold in the fresh or frozen raspberries. If you're using frozen raspberries, do *not* thaw them; just add them directly to the mixture. Tossing them in a tiny bit of flour first can help prevent them from sinking, but it's not strictly necessary for this recipe.
10. Carefully pour the raspberry lemon filling over the warm, pre-baked shortbread crust in the pan. Spread it out evenly with a rubber spatula so it covers the entire crust. Be gentle, you don't want to disturb the crust too much.
11. Return the pan to the oven and bake for another 25-30 minutes, or until the filling is set. How do you know it's set? Give the pan a gentle jiggle; the center should only slightly wobble, but not be liquid-y. The edges will look firm and a bit more golden.
12. Once baked, remove the pan from the oven and let the bars cool completely on a wire rack at room temperature. This is a crucial step! Do not rush it. Once cooled to room temperature, transfer the pan to the refrigerator and chill for at least 2-3 hours, or even better, overnight. This chilling time helps the bars firm up properly, making them easy to cut and ensuring that perfect, clean slice.
13. After thorough chilling, use the parchment paper overhangs to carefully lift the entire slab of bars out of the pan and onto a cutting board. Discard the parchment paper. Using a sharp knife, trim the edges (if you want super neat bars) and then cut the slab into squares or rectangles. For the cleanest cuts, wipe your knife clean between each slice, especially after the first few sticky ones. Dust with powdered sugar right before serving, if you like. Enjoy your little pieces of sunshine!