Preheat oven to 350 degrees with the rack in the middle.

Prepare the topping: Put butter and brown sugar in a 9-inch round cake pan, place the oven. As the sugar dissolves, stir once so the mixture spreads evenly over the pan. When the sugar starts to bubble and caramelize, remove pan from the oven and allow to cool.

In a small bowl, combine the cranberries and orange juice. Toss to coat berries well. Spread the berries evenly in the pan. Drizzle with any juice remaining in bowl. Set pan aside, and prepare the cake batter.

Prepare the batter: In a large mixing bowl, whisk together flour, baking powder, cinnamon, ginger and salt. Set aside.

Using an electric mixer with the paddle attachment, cream the butter and sugar together until pale, light and fluffy. Add vanilla, and beat in egg yolks one at a time, scraping bowl once or twice. Add flour mixture alternately with milk, ending with dry ingredients. Set batter aside.

Using electric mixer, whisk the egg whites with cream of tartar until whites are stiff enough to hold a slight peak.

Fold whites into batter 1/3 at a time. Spoon batter into prepared pan, and spread it evenly over cranberries. Bake until top is browned and cake pulls away slightly from edges of pan, 30-35 minutes (add 5-10 minutes if you live at high altitude). Test for doneness with a wooden skewer, cake is ready when it comes out virtually crumb free.

Let cake cool for 15 minutes before turning onto a serving plate. Top with the candied ginger. Serve with lightly sweetened whipped cream if desired.