1) Combine salmon, green peppers and onion in a bowl. Season with salt and pepper. Shape by hand into patties, as you would a hamburger. In a separate bowl, combine polenta and flour. Roll salmon patties in the polenta mixture.
2) Heat about 2cm of oil in a large, heavy skillet to 170C. Carefully place patties, in batches as necessary, in the hot oil and fry for 3 minutes on each side or until golden brown. Drain patties on kitchen towels. Serve with tomato ketchup and/or hot sauce, if desired.