Place the grated potatoes in a clean kitchen towel and squeeze out excess moisture. Transfer to a large mixing bowl.
Add the chopped onion, egg, flour, salt, pepper, and baking powder to the bowl with the potatoes. Mix until well combined.
Heat a large skillet over medium heat and add a tablespoon of butter.
Once the butter is melted and bubbling, scoop about 1/4 cup of the potato mixture into the skillet, flattening it slightly with the back of a spatula.
Cook for 3-4 minutes on each side or until golden brown and crispy. Repeat with the remaining mixture, adding more butter as needed.
Serve hot with a dollop of sour cream or a side of applesauce.