Preheat your oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper and spray with nonstick spray.

In a medium bowl, mix together flour, sugar, and salt for the crust. Cut in cold butter until mixture resembles coarse crumbs. Press two-thirds into the pan and bake for 10-12 minutes.

For the filling, zest and juice the lemons. Whisk together lemon juice, lemon zest, eggs, and sweetened condensed milk until smooth.

Pour lemon filling over baked crust gently. Sprinkle remaining crumb mixture on top.

Bake for 25-30 minutes until filling sets and topping turns golden brown.

Let cool at room temperature for about 30 minutes, then chill in the refrigerator for at least 2 hours.

Lift bars out using parchment overhang, slice into squares, and dust with powdered sugar if desired.