1/4 Onion
4 tbsp Mayonnaise
4 slices Sliced bread (thinly sliced)
Slice the onion and soak in water, then drain. Drain the oil from the canned mackerel and flake roughly with a fork. You can use the bread as-is or lightly toast it. Spread some mayonnaise over one side of each slice. Lay the mackerel on the bread and season with salt and black pepper. Then add the onion. Press gently so that the flavors would meld, then cut in half. So that the mackerel doesn't fall out when eating, press the sandwich down firmly and make sure to take big bites!