Put a piece of birch wood, large enough for the fish to sit on, in water for 24 hours. This step is important, if omitted your wood will catch fire.
Mix together all the Ingredients for the marinade.
Cut the fish into four equal parts without cutting through the skin.
Brush the top of the salmon generously with the marinade.
Season with salt and pepper according to taste.
Put the salmon on the wood and place directly on top of the fire. Leave to cook for about 25 minutes.
For the Salad: Divide the lettuce in two.
Cut the grapes in half and remove any remaining seeds.
Mix with the capers, the red onion, the oil and the vinegar.
Mix in the lettuce and season with salt and pepper.
Serve the salmon with the “Caper and Grape Salad”.