In a large pot, heat oil over medium heat sauté leeks, onion, garlic, red pepper for five minutes or until the onions are softened.
Then season with 1 tablespoon dill and ground black pepper.
Stir in sweet potatoes, corn and sauté for 5 more minutes.
Add water, bring to a boil over medium heat. Cover, reduce heat to medium-low and simmer for 5 minutes.
Increase heat to medium, stir in milk, salmon, dill, cilantro, parsley, chives.
Simmer, uncovered and stirring often but gently, for about 5 minutes or until salmon is firm and opaque and soup is thickened (do not let boil).
Stir in lemon juice and season to taste with pepper.
Ladle into warmed bowls and garnish with dill sprigs, chives and lemon zest.