The onions are first halved from top to bottom, then cut lengthways into thin wedges and sautéed in oil and butter over a mild heat for 5 minutes. Then the drained tuna is added and fried briefly.
Mix with curry and flour, continue cooking briefly. Add the broth and top up with the coconut milk. Let it simmer briefly, add the pineapple cut into pieces (two slices or to taste) and season with salt, pepper and a good dash of pineapple juice.