In a large pot, bring 4 quarts (16 cups) water to a boil with 2 tablespoons salt. Add the penne and cook until al dente, 10 to 12 minutes.
Meanwhile, in a saucepan of boiling water, blanch peas for 2 to 3 minutes, then drain. Frozen peas may take a minute more to cook.
Skin the salmon and cut into 1/2-inch cubes, removing any pin bones. In a sauté pan, heat 1 tablespoon olive oil, add the garlic and toss over medium heat for a minute or two. Add the salmon and toss gently until it changes color. Stir in the blanched peas. Season with sugar, salt and freshly ground pepper.
Drain the penne, return to the pot and toss in the remaining 2 tablespoons olive oil and melted butter. Add salmon mixture, herbs and freshly squeezed lemon juice, toss gently and season to taste. Transfer to a hot serving dish, sprinkle with lots of chopped dill weed and parsley, and serve.