Peel and grate sweet potato and apple. Before cooking, use a cheesecloth or strainer to extract as much of the liquid as possible.
Mix grated sweet potato, grated apple, egg, baking powder, cinnamon, flour, oat bran, flax seed meal, and salt in a large bowl.
Heat oil in a large skillet. Place a scoop of mixture in the skillet, and use the back of a spoon to flatten out the latke. Fry until golden brown, then flip and cook for another 2-3 minutes. Continue in batches.