Using a food processor fitted with a coarse grating disk, grate the potato and onion; discard any large pieces. Transfer the mixture to a clean dish towel and squeeze out any excess liquid then transfer to a large bowl. Stir in the flour, egg, 3/4 teaspoon salt, 1/4 teaspoon pepper and the baking powder.
In small bowl, whisk together creme fraiche, horseradish and a generous pinch of salt; cover and refrigerate.
To a food processor, add beets then combine with potatoes and onions. Add scallion greens and dill to batter.
In a medium skillet, heat 1/4 inch oil over medium-high heat until hot but not smoking. Working in 5 to 6 batches, drop 2-tablespoon scoops of batter into the pan about 2 inches apart. Using a spatula, flatten the batter into disks. Cook, turning once, until browned and crisp, about 5 minutes. (Lower the heat if the latkes darken too quickly.) Drain on paper towels. Serve with horseradish cream alongside.