Peel and coarsely shred 4 large potatoes with a hand grater. Grate 1 large onion. Combine in a large bowl.
Using a slotted spoon, press down the potato and onion mixture to squeeze out excess liquid. Tilt the bowl to discard the liquid.
\Add one egg, flour, baking powder, salt, and pepper to the bowl with potatoes and onion and mix well.
Heat a frying pan with frying oil, this will take about 5 minutes to reach a very high temperature. Test the oil with a piece of shredded potato, if it begins to fry and turn golden brown, the oil is ready for frying.
Begin to fry the latkes one spoonful at a time, using the slotted spoon to drain the additional liquid again before placing the latke in the frying oil. Carefully place the latke mixture in the frying oil (five latkes per batch, do not overcrowd).
Flatten the latkes in the skillet with the back of the spoon, and cook until the edges turn golden brown, about 2 minutes. Then, flip over and cook another minute until the bottom turns golden brown.
Place latkes onto a paper towel. Repeat with the remaining potato mixture. (You may need to add more oil to the skillet). Top with hummus and gravlax. Best when served warm and fresh out of the fryer.