Combine the crust ingredients in a food processor or with a pastry knife, but the food processor works best. Pulse until butter is fully mixed and the mix holds form when pressed.
Press crust into a parchment lined 9 x 13 pan until well compacted.
Bake for 20-25 minutes, or until the edges of the crust start to brown.
Keep oven at 350°F while you prep the filling and allow the crust to cool for 10 minutes.
Mix all filling ingredients with a whisk until fully combined. Pour over warm crust and bake for 20 minutes or until filling is firm.
Remove from oven and cool for 1 hour before lifting out the bars with the parchment paper. Allow to cool another 1 hour before slicing, OR chill for 2 hours. Dust generously with powdered sugar before serving.