Preheat the oven to gas 6, 200C, fan 180°C Put the salmon on a large piece of foil, drizzle with 1tbsp of oil, a squeeze of lemon and season. Fold up the sides of the foil to make a sealed parcel. Put on a baking sheet and roast in the oven for 20 minutes, until the fish is cooked through.
Meanwhile, cook the rice following the pack instructions. Drain and leave to cool. Bring a pan of water to the boil, add the beans, and blanch for 3 minutes, then drain and refresh in cold water.
Make a dressing by mixing together the remaining oil, lemon juice, mustard, and most of the dill, in a jug. Put the rice, beans, and cucumber in a bowl and pour over the dressing. Flake the salmon and toss through the rice, reserving a little extra to serve. Serve topped with the remaining salmon and dill.