📖 Instructions

1. **Before You Start (The Prep Work):** First thing's first, grab your favorite 9x13 inch baking pan. Line it with parchment paper, leaving a slight overhang on the sides. This little trick is a game-changer for lifting the bars out easily later. Give the parchment a light spray with non-stick cooking spray, just to be extra safe. Then, preheat your oven to 350°F (175°C). You want that oven nice and toasty when your crust goes in.
2. **Making the Shortbread Crust (The Foundation):** In a medium mixing bowl, combine the all-purpose flour, powdered sugar, and salt. Whisk these dry ingredients together thoroughly. Now, for the butter! Add your cold, cubed unsalted butter to the dry mix. Using a pastry blender, your fingertips, or a food processor (if you're feeling fancy!), cut the butter into the flour mixture until it resembles coarse crumbs. Think of it like wet sand – you should be able to press a small amount together, and it holds its shape. Be careful not to overmix; we want a tender crust, not a tough one.
3. **Pressing the Crust (Getting It Even):** Pour the crumbly crust mixture into your prepared 9x13 inch pan. Use the bottom of a flat-bottomed glass, your clean hands, or a small offset spatula to press the mixture down firmly and evenly across the bottom of the pan. Make sure it's packed tightly, especially in the corners. This prevents any sad, crumbly edges later.
4. **Baking the Crust (Golden Goodness):** Pop that pan into your preheated oven. Bake the crust for 18-20 minutes, or until the edges are lightly golden brown. It should smell wonderfully buttery in your kitchen! While the crust is baking, let's get a head start on the filling.
5. **Preparing the Lemon Raspberry Filling (The Zesty Heart):** In another medium mixing bowl, crack your large eggs and give them a good whisk until they're slightly frothy. Gradually add the granulated sugar to the eggs, whisking continuously until the mixture is well combined and the sugar starts to dissolve. Next, pour in the fresh lemon juice, add the 2 tablespoons of all-purpose flour, and the baking powder, along with the fragrant lemon zest. Whisk everything together until the mixture is smooth and completely combined. Make sure there aren't any lumps of flour hiding in there. The consistency should be pourable, like a thin custard.
6. **Adding the Raspberries (Sweet Surprises):** Gently fold in the fresh raspberries into the lemon filling. Be tender with them! We want them to stay mostly intact, not turn into mush. If you're using frozen raspberries, don't thaw them first; just add them directly to the filling to prevent them from breaking down too much.
7. **Pouring the Filling (Layering It Up):** Carefully remove the baked crust from the oven. It's going to be hot! Immediately pour the lemon raspberry filling evenly over the warm crust. The warmth of the crust helps the filling set beautifully. Gently spread it if needed, but try not to disturb the crust too much.
8. **Baking the Bars (The Grand Finale):** Return the pan to the oven. Bake for an additional 25-30 minutes. You'll know they're done when the filling is set—it won't jiggle much when you gently shake the pan. The edges might be slightly puffed and golden. Don't worry if the center still looks a little soft; it will firm up as it cools.
9. **Cooling Patience is a Virtue):** This is the hardest part, I swear! Once baked, remove the bars from the oven and let them cool completely in the pan on a wire rack. This can take at least 2-3 hours, or even longer. For the cleanest cuts and best texture, I highly recommend chilling them in the refrigerator for at least an hour after they've cooled to room temperature. Seriously, resist the urge to cut them warm; it'll be messy and less satisfying.
10. **Slicing and Dusting (The Finishing Touch):** Once completely chilled, use the parchment paper overhang to carefully lift the entire slab of bars out of the pan and onto a cutting board. Using a sharp knife, trim off the edges for a neat look (chef's treat!). Then, cut the slab into 12-16 squares or bars, depending on how generous you're feeling. Just before serving, dust them generously with powdered sugar. It adds a beautiful finish and a little extra sweetness. Now, go on, take a bite and enjoy your masterpiece!