Grease the slow cooker with 1 tablespoon / 15 ml (0.5 fl oz) of the ghee.
Arrange half the rutabaga slices in a single layer, season with salt and pepper, and drizzle with another tablespoon of ghee.
Add the remaining rutabaga slices in a second layer, season with salt, drizzle with the last tablespoon of ghee, and add the water or fish stock.
Place 2 layers of paper towels or a clean tea towel over the top of the slow cooker bowl to absorb condensation, then secure the lid.
Cook on low for 2 hours.
Place the salmon fillets on top of the cooked rutabaga.
Season with salt and pepper, sprinkle with fresh dill, and drizzle with lemon juice.
Replace the paper towel and lid, and continue to cook on low for 1 to 2 hours, or until the salmon is cooked to your liking. Start checking for doneness after 1 hour.
Stir in the heavy whipping cream or coconut milk during the last 30 minutes of cooking.
To serve, place a salmon fillet and a portion of the rutabaga on each plate.
Drizzle each serving with 1 tablespoon / 15 ml (0.5 fl oz) of extra-virgin olive oil. Store leftovers in an airtight container in the refrigerator for up to 3 days.
Don't overcook the salmon! Fish cooks quickly, even in a slow cooker.
Check for doneness after 1 hour by flaking it with a fork. It should be opaque and separate easily.