Sweet Potato Meringue Pie

From The Deen Bros. Y'All Come Eat

2 large sweet potatoes, baked and cooled
1 C sour cream
1 C granulated sugar
3 large eggs, separated
2 Tbsp unsalted butter, melted
2 Tbsp bourbon
1 tsp vanilla
1/2 tsp ground ginger
1/4 tsp ground nutmeg
1/4 tsp salt
All-purpose flour for dusting
1 Basic Flaky Single Piecrust (Pg 208 of cookbook), chilled, or 1/2 of a 15-ounce package rolled refrigerated unbaked pie crusts (1 crust)
1/4 tsp cream of tartar
1/2 C superfine sugar

Preheat oven to 350. Peel the potatoes and place in a large mixing bowl. Add the sour cream. beat on medium speed with an electric mixer until smooth. Beat in the granulated sugar, egg yolks, butter, bourbon, vanilla, ginger, nutmeg, and salt.
On a lightly floured surface, roll dough into an 11" circle. Line a 9" pie plate with the pie crust and crimp the edges decoratively. Pour the sweet potato mixture into the pie crust. Bake for 45-55 minutes or until almost set in the center. Let pie cool to room temperature.
Place the egg whites and cream of tartar in a second large mixing bowl. Beat on medium-high speed with an electric mixer until soft peaks form (tips curl). Add the superfine sugar, 1 tablespoon at a time, beating until the egg whites are stiff and glossy but not dry. Spoon the meringue over the pie filling; make sure to spread the meringue to the edges and use a spatula to form the customary meringue peaks. Bake at 350 for 10 minutes or until the meringue is golden. Let pie cool before cutting and serving.