Place the grated zucchini, onion and a sprinkle of salt in a bowl, and set aside for 20 minutes.
Squeeze as much of the liquid out of the zucchini mix as possible.
Sift the flour and baking powder into a large bowl. Add the egg and a few tablespoons of cold water to make a batter (not too thick).
Add the cabbage and the zucchini mixture, and stir to combine.
Heat some olive oil in a large frypan. Drop spoonfuls of the batter in and shape into a circle. Cook for 2 to 3 minutes each side, or until golden brown. Remove and place on some paper towel. Repeat until all the batter has been used.
To serve, drizzle the sauce and mayonnaise over the top of the fritters, and sprinke with spring onions and togarashi seasoning.