Peel and grate the sweet potato and rinse in a bowl of salted water. Using a sieve, drain the liquid, then pat dry with a tea towel and return to bowl. Peel and grate the onion, then squeeze out the excess moisture - do not rinse onion or you'll lose the flavor - and mix with sweet potato. Beat the eggs with pepper and add to the sweet potato/onion mixture; stir until coated.
In a non-stick pan, heat oil until it shimmers. Spoon potato mixture into small mounds onto the oil, then flatten with a fork. Repeat, stirring the potato mixture to recoat each time. Add more olive oil to the pan as needed.
When latkes are crispy and brown, flip with a spatula and sprinkle with salt to taste. Place on a paper towel-lined baking sheet in a low oven until all are done. Serve with applesauce and yogurt (an excellent substitute for sour cream).