Preheat oven to 350°F. Butter and flour a 9 inch springform pan or liberally spray with baking spray. Set aside.
In a medium-size mixing bowl, using a whisk, sift together flour, pudding mix, baking powder, baking soda and salt.
In a separate bowl, whisk together sour cream, butter, eggs and vanilla until fully combined.
Make a well in the center of the dry ingredients, Add the wet ingredients mixing with a large non-stick spoon or spatula until ingredients are fully combined. The batter will be stiff.
Toss cranberries with remaining 1 Tbsp flour until coated. Add to batter with white chocolate chips. Fold until evenly distributed.
Spread in prepared pan. Wrap bottom of pan with foil to prevent leaks.
Bake for 70-80 minutes or until a toothpick inserted into the center comes back clean. Check at 30 minutes and lay foil on top to prevent over browning.
Cool in pan for 30 minutes, then remove outer ring. Cool completely on a cooling rack.
Slice and serve dusted with powdered sugar. Store chilled.