Prepare the Crust and Crumble: In a large mixing bowl, combine all-purpose flour, granulated sugar, baking powder, and salt. Cut in the chilled, cubed unsalted butter until the mixture resembles coarse crumbs. Add the large eggs and mix until just combined.
Form the Base Layer: Press half of the crumb mixture firmly into the bottom of a greased 9x13-inch baking dish to form an even layer.
Create the Lemon Filling: In a separate bowl, whisk together fresh lemon juice, lemon zest, and sweetened condensed milk until smooth and well combined.
Assemble the Bars: Pour the lemon filling over the base layer in the baking dish, spreading it evenly. Sprinkle the remaining crumb mixture over the top of the lemon filling to create the crumble topping.
Bake to Perfection: Preheat your oven to 350°F (175°C). Bake the assembled bars for 25–30 minutes, or until the top is lightly golden and the filling is set.
Cool and Serve: Remove the baking dish from the oven and allow the bars to cool completely on a wire rack. Once cooled, cut into squares and serve.
