Place melted butter and mustard in a small dish and mix well.
Line a baking tray with aluminium foil and place individual pieces of salmon fillet on the tray. Season with salt to taste.
Spread a layer of the mustard mixture on top of each salmon fillet and season with pepper to taste.
Place the baking tray of salmon in the oven and bake for about 10-12 mins until salmon is cooked through and mustard browns.
While the salmon is baking, heat olive oil in a small pot over medium heat. Add shallots and sauté gently for about 2 mins till shallots are soft and fragrant.
Add lingonberry preserves, sweet sherry and red wine vinegar to the shallots and stir till preserves melt to form a sauce.
When the salmon is ready, plate the fish and spoon the sauce over to serve.