Fit an 8x8 inch pan with parchment paper or butter the pan.
Beat together the butter and sugar till creamy. Add the flour and salt and mix to combine- the mixture will be a bit crumbly. Press into prepared pan and bake for 15-20 minutes, until set and just golden.
Prepare the filling:
While the base cooks, add filling ingredients to a bowl and whisk to combine well.
Pour over the pre-baked crust and carefully return to the oven to bake for another 18 minutes, until the filling is set and the edges are lightly golden.
Let cool and cut into squares.
Dust with powdered sugar right before serving.
(the powdered sugar will melt on top once in the fridge so wait to dust if not served immediately.)
Storage: These will keep for 3-4 days in the fridge
To freeze: freeze immediately before or after slicing and let thaw on the counter. Dust with powdered sugar before serving.