Prep the Potatoes: In a medium saucepan, cover Yukon Gold potatoes with cool salted water and bring to a boil. Cook until tender, about 15 minutes. Drain, then ricer into a large bowl.
Grate the Baking Potatoes: While the Yukon Golds cool, peel and grate the baking potatoes. Squeeze out excess moisture with a kitchen towel. Add half of the grated potatoes to the riced potatoes.
Process Onion and Remaining Potatoes: In a food processor, combine the remaining grated potatoes and onion; pulse until finely chopped. Transfer to a fine-mesh sieve and press out excess liquid. Add this mixture to the large bowl with the riced potatoes. Stir in eggs, matzo meal, white pepper, and 2 teaspoons of salt.
Fry the Latkes: Heat ¼ inch of oil in a large skillet until shimmering. In batches, spoon ¼ cup of the potato mixture into the oil and flatten slightly. Fry over moderate heat, turning once, until golden and crisp, about 7 minutes. Drain on paper towels and sprinkle lightly with salt. Serve with applesauce.