Weigh or lightly spoon flours, potato starch, and flaxseed meal into dry measuring cups; level with a knife. Combine flours, potato starch, flaxseed meal, oats, and next 5 ingredients (through salt) in a medium bowl; stir with a whisk. Combine buttermilk, vanilla, and eggs in a medium bowl; stir with a whisk until blended. Add to flour mixture, stirring until smooth. Fold in cranberries.
Heat a nonstick griddle or large nonstick skillet over medium heat. Pour 2 tablespoons batter per pancake onto pan; cook 2 to 3 minutes or until tops are covered with bubbles and edges look cooked. Carefully turn pancakes over; cook 2 to 3 minutes or until bottoms are lightly browned. Sprinkle with powdered sugar.