Cut the onion and fennel into thin slices.
Heat the oil, then gently sauté the onion and fennel over low heat for 10 minutes under a lid. Stir occasionally.
Add the vinegar and stir for a couple of minutes, then add the stock. Cook for 5 minutes, then add the beans and bring to a boil.
Put the salmon fillets on top, squeeze the lemon juice on top, then season with salt and pepper.
Scatter most of the dill over the dish.
Put the lid on and cook for another 5-7 minutes, until the fish is tender. (The exact time depends on the thickness of the fish).
Stir in the dill and serve.