Debone the mackerel and cut it into bite-sized pieces.
Slice the onion and garlic thinly.
Boil the pasta in boiling water.
Heat olive oil in a pan and sauté the garlic and onion.
Add the mackerel and cook thoroughly.
Add the cooked pasta and a bit of pasta water, and stir-fry together.
Season with salt and pepper.
Plate and drizzle with olive oil.