Heat a 9-inch round cake pan over medium heat; coat pan with cooking spray. Add brown sugar and 2 tablespoons butter to pan, stirring until melted. Stir in ginger; cook 1 minute, stirring constantly. Remove from heat; arrange cranberries on top of brown sugar mixture.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, baking powder, and salt. Combine 1/4 cup butter and granulated sugar in a large bowl; beat with a mixer at high speed until fluffy. Add egg yolks, 1 at a time, beating well after each addition. Add flour mixture and milk alternately to butter mixture, beginning and ending with flour mixture; mix after each addition. Beat in vanilla.
Beat egg whites and cream of tartar with a mixer at medium speed until stiff peaks form. Fold egg whites into batter; pour batter over cranberries in prepared pan. Bake at 350° for 55 minutes or until a wooden pick inserted in center comes out clean. Cool in pan 15 minutes; run a knife around outside edge. Place a plate upside down on top of cake pan; invert cake onto plate. Top each serving with whipped topping.