Heat oven to 200° F. Coarsely shred potatoes and onion on a box grater or in a food processor. Combine in a colander or strainer and press out as much liquid as possible. Transfer to a large bowl and toss with lemon juice. Stir in garlic.
Add flour, eggs, salt and pepper. Stir to combine. Heat 1/4 cup of the oil in a 12-inch skillet over medium-high heat.
Scoop a scant 1/3 cup of the potato mixture into hot oil and press to flatten to 1/2 inch thick. Repeat, but do not crowd pan. Cook 2 to 3 minutes per side, until browned. Transfer latkes to a paper towel-lined baking sheet and keep warm in 200° F oven. Repeat with all of the potato mixture, adding remaining 1/4 cup oil to pan halfway through.
Serve latkes with sour cream and applesauce alongside.