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Cut lemon bar squares showing distinct creamy layers and crumb topping resting on parchment paper

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Brown Butter Lemon Crumb Bars

Recipe by Chloe Davis

The secret to elevating a classic lemon bar is swapping standard melted butter for nutty, deeply aromatic brown butter in the crust. Paired with a sharply tart, silky lemon filling and a pinch of flaky sea salt, these oat crumb bars hit the perfect balance of bright citrus and rich, caramelized flavor.

  • Total Time3 hours 57 minutes
  • Yield16 bars (serves 16) 1x

Ingredients

Scale

Brown Butter Oat Crust & Topping

  • 1/2 cup unsalted butter (1 stick / 113g)
  • 1 cup all-purpose flour (125g)
  • 3/4 cup old-fashioned rolled oats (65g)
  • 1/2 cup packed light brown sugar (100g)
  • 1/2 teaspoon kosher salt
  • 1/2 teaspoon baking soda
  • Flaky sea salt, for finishing

Creamy Lemon Filling

  • 1 can (14 oz) sweetened condensed milk
  • 1/2 cup fresh lemon juice (120ml), from about 3 large lemons
  • 1 1/2 tablespoons finely grated lemon zest
  • 2 large egg yolks
  • 1 teaspoon pure vanilla extract

Instructions

  1. Preheat and prep: Heat your oven to 325°F (165°C). Line an 8×8-inch baking pan with two crisscrossing sheets of parchment paper, leaving enough overhang on the edges to easily lift the bars out later. Lightly grease the parchment.
  2. Brown the butter: Place the butter in a small saucepan over medium heat. Melt the butter, then continue cooking, swirling the pan constantly. It will foam up, then eventually subside and reveal toasted brown bits at the bottom. As soon as it smells nutty and the solids are golden brown (about 4 to 5 minutes), immediately pour the butter—including all the toasted bits—into a large mixing bowl to stop the cooking. Let it cool for 5 minutes.
  3. Mix the crust: To the bowl with the warm brown butter, add the flour, oats, brown sugar, kosher salt, and baking soda. Stir until the mixture resembles damp sand and holds together when squeezed.
  4. Par-bake the base: Reserve about 3/4 cup of the crumb mixture for the topping. Pour the remaining mixture into your prepared pan, pressing it firmly and evenly into the bottom. Bake for 15 minutes, until fragrant and just beginning to set.
  5. Whisk the filling: While the crust bakes, whisk the sweetened condensed milk, fresh lemon juice, lemon zest, egg yolks, and vanilla extract in a medium bowl until completely smooth and slightly thickened.
  6. Assemble and bake: Remove the pan from the oven and immediately pour the lemon filling over the hot crust, spreading it into the corners. Evenly scatter the reserved 3/4 cup of oat crumbs over the top. Return the pan to the oven and bake for 20 to 22 minutes, until the edges are lightly golden and the center of the lemon filling is set but still has a slight jiggle.
  7. Cool and chill: Transfer the pan to a wire rack. Sprinkle lightly with flaky sea salt while still warm. Let the bars cool completely to room temperature (about 1 hour), then cover and chill in the refrigerator for at least 2 hours before slicing into squares.

Notes

  • Why it works: The acidity in the lemon juice naturally thickens the sweetened condensed milk without the need for flour or cornstarch. The egg yolks act as structural insurance, ensuring the filling sets into a creamy, perfectly sliceable layer rather than weeping into the crust.
  • Slicing tip: For the cleanest cuts, pull the bars out of the pan using the parchment overhang and slice them while they are completely cold, wiping your knife with a damp paper towel between each cut.
  • Storage: These bars actually improve on the second day as the oat crust softens slightly and the lemon flavor ripen. Store them in an airtight container in the refrigerator for up to 5 days.

Nutrition (per serving — estimates)

Calories: 209 | Total Carbs: 29g (Fiber: 1g, Sugar: 21g) | Fat: 9g (Saturated: 5g) | Protein: 3g

Nutritional values are approximate, based on standard reference data (USDA FoodData Central). Actual values vary by brand and exact measurements. For precision, use a tracker like MyFitnessPal or Cronometer.

  • Prep Time: 20 minutes
  • Cooling Time: 1 hour
  • Cook Time: 37 minutes
  • Category: Dessert
  • Method: Baking
  • Cuisine: American

Nutrition

  • Serving Size: 1 square
  • Calories: 209
  • Sugar: 21g
  • Fat: 9g
  • Saturated Fat: 5g
  • Carbohydrates: 29g
  • Fiber: 1g
  • Protein: 3g

Find it online: https://delicious.alfityan.org/2026/08/24/brown-butter-lemon-crumb-bars/