In a large pot, melt the butter over medium heat. Add the diced onion and sauté until translucent, about 5 minutes.
Add the sliced carrots and diced potatoes to the pot. Cook for an additional 5 minutes, stirring occasionally.
Pour in the fish stock or vegetable broth and bring to a boil. Reduce heat and simmer until the vegetables are tender, about 15 minutes.
Stir in the heavy cream, salmon pieces, and dried dill. Cook for another 5-7 minutes, or until the salmon is cooked through.
Season with salt and pepper to taste.
Serve hot, garnished with fresh dill and lemon wedges on the side.