Creating Key Lime Pie Bars – Browned Butter Blondie is simple if you follow these step-by-step instructions:

1. Preheat Oven: Begin by preheating your oven to 350°F (175°C). Grease a 9×9-inch baking pan or line it with parchment paper for easy removal.

2. Brown the Butter: In a medium saucepan over medium heat, melt the butter. Continue cooking it until it turns golden brown and develops a nutty aroma. Remove from heat and let cool slightly.

3. Mix Blondie Batter: In a large bowl, combine the browned butter and brown sugar, mixing well. Add the eggs and vanilla extract, stirring until smooth. In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add this dry mixture to the butter mixture, stirring until just combined.

4. Pour Blondie Layer: Pour the blondie batter into the prepared baking pan, spreading it evenly. Bake for 25-30 minutes or until a toothpick inserted in the center comes out clean. Allow to cool for about 15 minutes.

5. Prepare Key Lime Filling: In a separate bowl, whisk together the sweetened condensed milk, key lime juice, egg yolks, and lime zest until smooth.

6. Add Key Lime Filling: Pour the key lime mixture over the slightly cooled blondie layer. Bake for an additional 15 minutes, until the filling is set but still slightly jiggly in the center.

7. Cool and Slice: Remove the bars from the oven and allow them to cool completely at room temperature. Once cooled, cover them and refrigerate for at least 1 hour. Finally, slice into squares.