Rinse the grated potatoes in a bowl of cold water. Remove the potato shred with your fingers to a clean kitchen towel. Roll up in the towel and squeeze dry.
Place the beets and onions in a large colander and strongly squeeze out the excess moisture.
In a bowl, stir together the potato, beets, onion, eggs, flour, salt, and pepper to taste.
Heat 1/4 cup of the canola oil in a cast-iron skillet over medium-high heat. Add 4 heaping tablespoons of batter to the pan to form 4 pancakes; flatten slightly. Cook about 5 minute, turning once, until golden brown on both sides. Keep warm on a rack set over a baking sheet in a low oven. Repeat with the remaining potato mixture and 1 1/3 tablespoons of oil.
Top each pancake with a teaspoon of sour cream or yogurt and sprinkle with fresh dill. Serve at once.
Recipe courtesy of Joel Patraker and Joan Schwartz, The Greenmarket Cookbook, Penguin Putnam Inc. 2000