1-Step 1: Prepare Your Equipment Before you begin mixing anything, preheat your oven to 325°F. This moderate temperature is key to baking the filling evenly without overcooking the edges. Line a 9×13 glass or ceramic pan with parchment paper, leaving an overhang on the sides. This overhang acts as handles, making it easy to lift the entire slab of bars out of the pan for clean, neat cutting.

2-Step 2: Make the Shortbread Crust In a medium mixing bowl, combine the melted butter, granulated sugar, vanilla extract, and salt. Whisk until fully combined and smooth. The mixture should look glossy and well-blended. Add the flour to your butter mixture. Using a spatula or wooden spoon, stir until just combined. The dough will be thick and slightly crumbly, which is exactly what you want for a tender shortbread texture. Press the dough evenly into your prepared pan. Work from the center outward, making sure the crust reaches all corners and edges. The layer should be uniform in thickness for even baking.

3-Step 3: Bake the Crust Place the pan in your preheated oven and bake for 20-22 minutes. You’re looking for the edges to become lightly browned, while the center should still look pale but set. When you remove the crust from the oven, immediately poke holes across the entire surface using a fork. These holes serve an important purpose: they allow the lemon filling to seep slightly into the crust, creating a stronger bond between the two layers and preventing that dreaded separation when you cut into your bars.

4-Step 4: Prepare the Lemon Filling While the crust bakes, whisk together the sugar and flour in a large bowl. Sifting them together helps prevent any flour lumps in your finished filling. Add the eggs, fresh lemon juice, and lemon zest (if using). Whisk gently but thoroughly until completely smooth.

5-Step 5: Combine and Bake Pour the lemon filling directly over your warm, freshly baked crust. The warmth helps the filling begin to set immediately, creating a seamless layer. Return the pan to the oven and bake for 22-26 minutes. You’ll know your bars are done when the edges are set and the center has just a slight wobble when you gently shake the pan. Think of it like gelatin: it should move as one piece rather than ripple like liquid.

6-Step 6: Cool and Chill Patient cooling is the secret to perfect lemon bars. Let your pan cool at room temperature for about 2 hours. This gradual cooling helps prevent cracks from forming on the surface. After the room temperature cooling, transfer the pan to the refrigerator and chill for 1-2 hours. This step is non-negotiable: the bars need that cold setting time to achieve their signature texture. Skip this, and you’ll end up with a gooey mess rather than clean, beautiful squares.

7-Step 7: Serve and Enjoy Use the parchment paper overhang to lift the entire slab out of the pan. Place it on a cutting board and use a sharp knife to cut into 24 bars. Wipe the knife clean between cuts for the neatest edges. Just before serving, dust generously with confectioners’ sugar. This snowy white layer adds a beautiful visual contrast and a hint of extra sweetness. If you love make-ahead desserts like our lemon tiramisu, you’ll appreciate how well these bars keep.