Preheat the oven to 200°F. Place a wire rack over a baking sheet and set aside.

Using the large holes on a box grater, grate potatoes and onion. (Feel free to use a food processor if you prefer.) Place processed potatoes and onions in a large bowl of cold water and swirl them around to get as much starch off the potatoes as possible. Drain the potato mixture and place in a clean towel. Squeeze as much liquid out of the potato shreds as possible. With the excess moisture removed, transfer the potatoes to a medium bowl. Add the eggs, flour, salt, pepper, baking powder, garlic, and green onions and stir to combine.

Pour about 1/2 inch of oil into a large cast-iron skillet over medium to medium-high heat. When the oil is shimmering, scoop potato mixture into a ball a little larger than a golf ball and place the batter into the hot oil. Flatten to make 2- to 3-inch-wide latkes. Repeat and add more latkes to the pan keeping them about 2 inches apart. Cook for about 3 to 4 minutes per side, or until nicely browned. Flip the latkes with a spatula and cook on the other side for another 2 to 3 minutes longer.

Transfer cooked potato latkes to the wire rack on the baking sheet. If you like, you can pat off some of the oil with paper towels before putting the baking sheet in the 200 degree oven to warm. Repeat with the remaining latkes in batches. Transfer latkes to a paper towel-lined plate or platter and serve immediately with the creamy lox sauce.