Peel potatoes, then shred on the large holes of a box grater.
Rinse shreds briefly in cold water, drain, and squeeze very dry in a clean towel.
Grate the onion and press out excess liquid.
Combine potatoes, onion, eggs, flour, baking powder, salt, pepper, and garlic powder in a bowl.
Stir until the mixture holds together but isn’t pasty; adjust salt to taste.
Heat a large skillet over medium heat and add a thin layer of oil.
Scoop 1/4-cup mounds into the pan, flatten gently to 1/3 inch thick.
Fry until deep golden and crisp, 3–4 minutes per side. Drain on a rack; repeat with remaining batter.