Melt 3 tablespoons butter in a large skillet over medium heat. Add onion, and cook 20 minutes, stirring often. Add 1 1/2 cups of wine, bell pepper, and brown sugar; cook 20 minutes or until onion is tender, stirring often.
Add olives, and cook 5 minutes, stirring often. Remove from heat, and keep warm.
Combine remaining wine, fish broth, garlic, and bay leaf in a deep skillet or Dutch oven; bring to a simmer. Add salmon, skin-side down. Cover and simmer 7 minutes or until fish flakes easily with a fork. Remove to a serving platter with a slotted spatula.
Pour 1 cup poaching liquid into a small saucepan; bring to a boil. Simmer, uncovered, until liquid reduces to 1/3 cup. Remove from heat, and stir in remaining 1 tablespoon butter, parsley, and pepper. Spoon 1/2 cup onion confit over each salmon fillet; drizzle with butter-parsley sauce.