Remove the skin from your fish then blend it with the onions in a food processor, it will look like mush
In a large bowl, mix the ground fish mixture, eggs, matzo meal, salt, pepper, and sugar until smooth.
Chill the mixture for 30 minutes to make it easier to handle.
Using wet hands, shape the mixture into your preferred sized cakes
Heat oil in a frying pan
Fry the fish cakes in batches, about 6–7 minutes per side, until golden brown and cooked through
Transfer to a paper towel-lined plate to drain the excess oil