Lemon Buttermilk Pie Bars with Shortbread and Curd Swirl

Why You’ll Love This Recipe

• Buttery, tender shortbread base that melts in your mouth.
• Bright lemon-buttermilk custard that’s silky, tangy, and not too sweet.
• Gorgeous lemon curd swirl for bakery-shop looks and extra zing.
• Finishes with a light snowfall of powdered sugar for classic charm.

Grocery List

• Produce: 3 medium lemons
• Dairy: Unsalted butter, buttermilk, large eggs
• Pantry: All-purpose flour, cornstarch, granulated sugar, powdered sugar, fine sea salt, vanilla extract, parchment paper

Full Ingredients

Shortbread Crust

• 1 1/4 cups (150 g) all-purpose flour
• 1 tbsp (8 g) cornstarch
• 1/3 cup (40 g) powdered sugar
• 1/2 tsp fine sea salt
• 10 tbsp (140 g) cold unsalted butter, cut into small cubes

Lemon-Buttermilk Filling

• 3/4 cup (150 g) granulated sugar
• 3 tbsp (24 g) all-purpose flour
• 1/8 tsp fine sea salt
• 3 large eggs, at room temperature
• 1 large egg yolk, at room temperature
• 3/4 cup (180 ml) well-shaken buttermilk
• 1/3 cup (80 ml) fresh lemon juice
• 1 tbsp finely grated lemon zest
• 3 tbsp (42 g) unsalted butter, melted and slightly cooled
• 1 tsp pure vanilla extract

Bright Lemon Curd Swirl

• 1 large egg yolk
• 1/4 cup (50 g) granulated sugar
• 3 tbsp (45 ml) fresh lemon juice
• 1 tsp finely grated lemon zest
• Pinch fine sea salt
• 2 tbsp (28 g) unsalted butter, softened
• Shortcut option: 1/2 cup (120 g) good-quality store-bought lemon curd

To Finish

• 2 tbsp powdered sugar, for dusting
• Fine strips of lemon zest, for garnish (optional)

Step-by-Step Instructions

Step 1: Preheat and prepare the pan

Heat the oven to 350°F (175°C) with a rack in the center. Line an 8-inch (20 cm) square metal baking pan with a parchment sling, leaving overhang on two sides for easy removal. Lightly mist or butter the pan so the parchment sticks flat.

Step 2: Make the shortbread base

In a bowl, whisk the flour, cornstarch, powdered sugar, and salt. Cut in the cold butter with a pastry cutter or rub with fingertips until sandy and the dough holds together when squeezed. Alternatively, pulse everything in a food processor 8–10 times. Tip the mixture into the pan and press firmly into an even layer, reaching the corners. Dock with a fork. Chill 15 minutes to prevent shrinkage.

Step 3: Par-bake the crust

Bake the chilled crust for exactly 20 minutes, until the edges are lightly golden. While it bakes, prepare the lemon curd swirl and the filling so they’re ready when the crust comes out hot.

Step 4: Cook the quick lemon curd swirl

In a small saucepan, whisk the egg yolk, 1/4 cup sugar, 3 tbsp lemon juice, zest, and a pinch of salt. Cook over medium-low heat, whisking constantly, until thickened and the mixture reaches 170°F (77°C), 4–6 minutes. Remove from heat and whisk in the 2 tbsp butter until glossy. Scrape into a small bowl and press plastic wrap directly on the surface. Let cool 10 minutes; it should be thick but dollop-able. (Or use 1/2 cup store-bought lemon curd.)

Step 5: Mix the lemon-buttermilk filling

In a medium bowl, whisk the sugar, flour, and salt. Add the 3 eggs and 1 yolk; whisk smooth. Whisk in the buttermilk, then lemon juice, zest, and vanilla. Finally whisk in the melted butter. Strain the custard through a fine-mesh sieve into a spouted measuring cup to catch any bits of zest or bubbles. Let sit 5 minutes so bubbles dissipate.

Step 6: Assemble and bake

Pour the custard over the hot crust. Dollop about 1/2 cup lemon curd over the surface in 9–12 spoonfuls. Drag a skewer or butter knife through the dollops to create a loose marble pattern; avoid over-swirling. Return to the oven and bake for exactly 22 minutes, until the edges are set and the very center has a gentle wobble when jiggled. Do not overbake—carryover heat will finish the set.

Step 7: Cool, dust, and slice

Cool the pan on a wire rack for 60 minutes, then refrigerate until fully set, at least 60 minutes more. Lift out using the parchment. Dust generously with powdered sugar. Trim the edges for neatness (snack on the trimmings), then cut into 16 squares, wiping the knife clean between cuts. Garnish with fine lemon zest strips if you like.

Pro Tips

• Room-temperature eggs and buttermilk whisk more smoothly and minimize curdling.
• Straining the custard makes an ultra-silky filling and removes air bubbles for a smooth top.
• Use a light-colored metal pan for even baking; glass may require a few extra minutes.
• For clean swirls, dollop distinct spoonfuls of curd and make gentle figure-eights with a skewer.
• Chill before slicing—warm custard will smear and won’t cut into clean bars.

Variations

• Meyer Lemon Bars: Swap standard lemons with Meyer lemons for a sweeter, floral tang.
• Raspberry-Lemon Swirl: Swap the lemon curd swirl for 1/2 cup seedless raspberry jam loosened with 1–2 tsp lemon juice.
• Coconut Shortbread: Replace 1/3 cup (40 g) of the flour in the crust with finely shredded unsweetened coconut.

Storage & Make-Ahead

Refrigerate bars in an airtight container, layered with parchment, for up to 4 days. Dust with powdered sugar just before serving. Freeze individually wrapped bars (without powdered sugar) in a freezer-safe bag for up to 2 months; thaw overnight in the refrigerator and dust before serving. The lemon curd swirl can be made up to 1 week ahead and refrigerated.

Nutrition (per serving)

Approximate for 1 of 16 bars: 230 calories; 12 g fat; 28 g carbohydrates; 17 g sugars; 3 g protein; 0.5 g fiber; 85 mg sodium.