1.Shred the potatoes and onion in a food processor. Place in a strainer that has been lined with cheesecloth. Toss with 3/4 teaspoon salt and let sit over a bowl to drain for 30 minutes.
2.Gather the top of the cheesecloth and use your hands to squeeze out as much excess moisture as you can. Transfer the vegetables to a clean bowl; mix in the eggs, lemon juice, flour and some pepper.
3.Heat in a large skillet over medium heat until shimmering. Working in batches so as not to crowd the pan, fry loosely packed rounded tablespoons of the potato mixture until browned, about 2 minutes per side. Add more oil to the pan and adjust the temperature as needed. Transfer to a rack and season with salt while hot. Serve immediately.