Mix potatoes, onions, eggs, flour, baking powder, and lemon juice in a large bowl; season with nutmeg, salt, and black pepper. Shape potato mixture into 12 evenly sized patties.
Heat vegetable oil in a large skillet over medium heat. Pan-fry potato patties in batches until tender and browned on both sides, 7 to 10 minutes. Transfer browned patties to a paper towel-lined baking sheet. Repeat with remaining patties.