Preheat your oven to 350°F (175°C) and prepare a 9x9-inch baking pan by greasing it and lining it with parchment paper, leaving some overhang.

In a large mixing bowl, combine the all-purpose flour, granulated sugar, light brown sugar, salt, and baking powder. Mix until well incorporated, then add the cooled melted butter and blend until crumbly. Press about ¾ of this mixture into the pan and bake for 15 minutes or until lightly golden.

In another bowl, whisk together the sweetened condensed milk, egg yolks, heavy cream, and salt. Gradually whisk in the fresh lemon juice until well combined and creamy.

Pour the lemon filling over the warm crust, spreading evenly. Sprinkle the remaining crumb mixture on top and bake for an additional 15-20 minutes until golden brown and filling is slightly soft in the center.

Allow to cool completely at room temperature for about an hour, then refrigerate for at least 4 hours before slicing into squares.