Preheat the barbecue to a medium heat, or if using charcoal allow the flames to die down until the coals are grey.
Rinse salmon and pat dry. Brush a big piece of aluminium foil with olive oil and place salmon on top with the skin side down. Brush salmon with oil and sprinkle with salt and pepper. Seal the foil parcel.
Barbecue for 15 to 20 minutes, depending on the thickness of the fillet.
For the dill sauce:
Meanwhile prepare the dill sauce. Combine soured creme, cream cheese and mustard in a medium bowl and vigorously whisk them together. Stir in dill and garlic powder and season with salt and pepper to taste.
Return to the barbecue and open the foil packet and let it sit on the grate for a few more minutes until the salmon is evenly pink throughout. Remove the fish from the barbeceue, transfer to a serving plate and top with a dollop or two of the dill sauce and serve.