Bring a pot of water to a boil, add the asparagus, and blanch for 1 minute. Drain and set aside.
Put 2 tablespoons butter in a skillet over a medium-high heat. (I find a nonstick pan is foolproof.) Salt the salmon and sauté in the butter for about 2 - 3 minutes; turn and cook another 2 - 3 minutes, or until the fish is opaque and flakes easily with a fork. Remove the fish to a dish and keep warm.
Add the remaining 2 tablespoons of butter and the optional sesame oil to the skillet, reduce the heat to medium, and add the asparagus. Cook for about 3 - 4 minutes, until crisp-tender. Serve the salmon and asparagus with the lemon wedges.