Preheat oven to 350 degrees. Place rack in center of oven. Place a glass or metal pan filled with water on bottom of oven. This will make a moister cake.
Lightly mist a 12 cup Bundt pan with vegetable oil spray, then dust with flour. Shake out the excess flour, then set aside.
Melt butter. Stir in sugars, vanilla, eggs, gingers and baking soda. Add baking soda in pinches. Break up the lumps by rubbing with your fingers. Stir in buttermilk. At this point to ensure a good mix you could beat the batter.
Stir in corn starch and flours until just well blended. Once you have added flour you do not want to "mess with" the batter. The more you stir your batter after you have added the flour, the tougher your cake will become. Pour into cake pan, tap the pan once or twice on the counter to get any air bubbles out of the cake batter.
Start to check on the cake after 60 minutes of baking time. With the pan of water in the oven it may take up to 75-80 minutes of baking time. When done you should be able to smell the cake, look for the sides of the cake to pull away from the pan and finally test the center of the cake with a cake tester.
Cool the cake for 20 minutes. Invert cake on plate. Cool completely.
Serving suggestions: dust with powdered sugar, lemon powdered sugar. Serve with Cool Whip, whipped cream, vanilla/butter sauce or lemon sauce. Frost with lemon frosting or icing or a cream cheese icing.