Preheat 350 degrees.
For crust, cream together the butter and sugar. Add flour, salt and mix. Place in a parchment lined 8x8 baking pan and press out evenly.
For the filling, whisk together all ingredients until combine. Set aside.
Bake crust for 10 minutes or browned.
Spread filling and bake for additional 18-20 minutes or until set.
Let cool and refrigerate to store.