Preheat oven to 325°. Place the prebaked pie shell on a baking sheet, brush with egg wash and set aside.
In large bowl, stir together the sugar, cornmeal, flour and salt. In a separate bowl mix the melted butter with the eggs, 1 at a time, stirring well after each addition. Mix briskly until the filling is thick and light colored. Stir in the heavy cream, followed by the lemon juice, orange juice and vanilla extract. Add to the sugar mixture. Strain the filling through a fine-mesh sieve directly into a bowl. Add citrus zest and pour into prepared shell. Bake for 40 minutes, rotating once then continue baking for 30-35 minutes. You will know it's done when the top is slightly golden and has a slight wiggle in the center. Do not overbake; the filling will continue to cook and set as it cools. Allow to cool completely on a wire rack, 3-4 hours.
TIP: We love to use local citrus. I use a combination of grapefruit, blood orange and various oranges. Just be sure to balance with lemon juice and adjust the sugar if needed.