Cut the fresh salmon into small cubes. Mix it and marinade in 50 millilitres of lime juice, a drizzle of olive oil little and a pinch of salt for 30 minutes, and place to one side.Meanwhile, chop the spring onions and the peeled, seedless tomato. Dice the avocado, place it all in a bowl and add the lime juice.Presentation: using a ring mould, place the avocado salad at the bottom, then the tartar salmon and top with the salmon roe. Place the moulds on plates and remove the ring. Serve the salmon tartar with avocado with a rocket salad and toast.