Preheat oven to 350°F. Grease a 8"x8" baking pan.
Whisk together dry ingredients in a mixing bowl. Add the chilled butter slices and work together with hands until evenly combined. Mixture should be crumbly.
Press into the bottom of the pan then bake for 10 minutes, until slightly browned.
Meanwhile, prepare the filling. Whisk together all ingredients until combined.
Remove the baked crust and pour the filling over it. Return to the oven and bake for 15 minutes until filling is set.
Remove from the oven and let cool in pan. Dust with powdered sugar. Cover and refrigerate until ready to serve.
