In food processor, combine the onion and eggs and puree until smooth and fluffy. Add the potato and pulse mixture until pureed, leaving some chunks. Add the salt, pepper, and flour and process to combine – do not over process.
Place mixture in a wire colander and using the back of a large spoon, gently press to drain any excess liquid.
Preheat oven to 300. Line a large baking sheet with a double layer of paper towels.
Heat ½” of oil into a large cast iron skillet over medium-high heat. Spoon rounded tablespoons of the mixture into the oil, making sure they don’t touch. Flatten with the back of a spoon.
Fry until golden brown, about 2 minutes on each side. Transfer to the prepared baking sheet to drain and place in the oven until all are cooked.