This humble pie has a special twist: it divides into two layers, the tart rhubarb on top and the creamy custard on the bottom.
Preheat oven to 375 degrees F. Prepare pie crust by placing it in a standard 9″ deep dish pie pan and refrigerate as the pie is made and oven preheats.
Place egg whites in mixing bowl and beat until soft peaks form. Set aside. In another mixing bowl (no need to rinse beaters) Add eggs, sugar, butter, flour, orange juice concentrate, baking powder, and salt. Beat until lightened in color. Stir in rhubarb.
Fold the egg whites into the batter, starting with about 1/3 of the eggs whites, mixing until incorporated, then gently adding the rest in two additions. Scrape filling into pie crust. Place in oven and bake for 15 minutes, then turn oven down to 325 degrees F. and bake an additional 40 to 45 minutes until the pie is puffed and top is a medium golden brown.
Remove and cool at room temperature for an hour, then refrigerate. Serve pie cold or remove from refrigerator and let sit at room temperature for about 20 to 30 minutes before serving.
If you don’t have orange juice concentrate, the pie is just as good without or you can add the zest of an orange and two tablespoons of the juice to the pie instead.