2. Peel the potatoes and onion and coarsely grate in a food processor fitted with a shredding disk, or on a box grater. Grab handfuls of the grated vegetables and squeeze tightly between your fingers to wring out as much liquid as possible.
3. Transfer the grated vegetables to a mixing bowl and stir in the flour, baking powder, egg substitute and a pinch of salt and pepper. (The potato pancakes should be highly seasoned.)
4. Spray the hot griddle with oil (or drizzle the oil on it and spread with a wooden spoon.) Spoon small mounds of potato mixture onto the baking sheet to form 3-inch pancakes, leaving 1 inch between each. Fry the pancakes on the griddle until golden brown, 6 to 8 minutes per side, turning once with a spatula.
5. Transfer to plates or a platter and serve immediately with sour cream and/or applesauce.