1Dissolve vitamin C tablet in 2 tablespoons hot water in a small bowl.
2Shred the potatoes using first the shredding blade and then the metal blade of the processor (or use a hand shredder). Place in bowl with vitamin C.
3Shred the onion in the food processor just as you shred the potato; add to potatoes. Stir in the eggs, salt, baking powder, and matzah meal until incorporated.
4Pour 1/4 to 1/2 inch oil into a large skillet and heat over medium-high heat. Once oil is to temperature (you can check by sticking a wooden utensil into the oil and seeing if bubbles form), spoon 2 tablespoons potato mixture into hot oil. Do not crowd. Flatten slightly with the back of the spoon.
5Fry pancakes until golden on both sides, turning once. When you reach the end of the batter, pat the mixture with a paper towel to remove excess liquid.
6After frying, remove the pancakes to paper towels to drain. Serve with applesauce and/or sour cream, if desired.