Preheat oven to 350°F and line a 9×9-inch pan with parchment paper.
In a large bowl, combine oats, flour, brown sugar, baking soda, and baking powder. Pour in melted butter and mix until crumbly.
Press half of the mixture into the pan and bake for 12–15 minutes until golden.
In another bowl, whisk condensed milk, lemon juice, yolks, zest, and salt until smooth.
Pour the lemon filling over the baked crust, then sprinkle the remaining crumbs on top.
Bake for 20–25 minutes until the top is golden brown.
Let cool to room temperature, then refrigerate 1 hour before slicing.
