Preheat the oven to 400°F. Line a baking sheet with foil.
Scrub and dry the sweet potatoes. Pierce each one several times with a fork and place them on the prepared baking sheet.
Bake for 50 to 70 minutes, or until completely tender when pierced through the center.
Allow the potatoes to cool until they are safe to handle. Remove the skins and measure 2 packed cups of sweet potato flesh.
While the potatoes cool, fit the pie crust into a 9-inch deep-dish pie plate. Trim and crimp the edges. Refrigerate for 20 to 30 minutes.
Reduce the oven temperature to 375°F. Line the chilled crust with parchment paper and fill it with pie weights or dry beans.
Bake for 12 minutes. Carefully remove the parchment and weights, then bake for another 4 to 5 minutes. Set aside.
Reduce the oven temperature to 350°F.
Place the warm sweet potato flesh in a large mixing bowl. Beat with an electric mixer for about one minute, or until smooth.
Add the melted butter, brown sugar, and granulated sugar. Beat until evenly combined.
Add the eggs one at a time, mixing briefly after each egg.
Add the evaporated milk, vanilla, cinnamon, nutmeg, ginger, salt, and optional orange zest.
Mix on low speed just until smooth. Scrape the sides and bottom of the bowl.
Pour the filling into the partially baked pie crust and smooth the top.
Bake for 50 to 60 minutes. Cover the crust edges with foil if they begin browning too quickly.
Remove the pie when the edges are set and the center still has a gentle jiggle.
Cool on a wire rack for at least three hours before slicing.
Serve at room temperature or chilled with whipped cream, if desired.