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 matzah meal, baking powder, egg substitute, parsley, and plenty of salt and pepper. (The latkes should be highly seasoned.)
4. Spray the hot baking sheets 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 2-1/2 inch pancakes, leaving 1 inch between each. Bake-fry the latkes in the oven until golden brown, 6 to 8 minutes per side, turning once with a spatula. (When you turn the latkes, try to flip them onto spots on the baking sheet that still have oil.)
5. Transfer to plates or a platter and serve immediately with sour cream and/or applesauce.