Mix crème fraîche and lemon juice. Season with salt and pepper. Halve the avocado and remove the stone. Peel the flesh. Cut avocado halves into 6 slices. Arrange salmon ham on plates.
Place the avocado slices on top and add a dash of crème fraîche to each. Cut the cress from the bed and sprinkle over it. Delicious with baguette.