Remove roots, outer leaves, and tops from leeks. Cut leeks in half lengthwise. Rinse thoroughly with cold water, and cut each half into 3 inch julienne strips.
Melt butter in a large nonstick skillet over medium heat. Add leeks to pan; cook 4 minutes or until slightly wilted, stirring occasionally. Stir in brown sugar and 1/4 teaspoon salt; cook 20 minutes or until edges are browned, stirring occasionally. Remove from heat: stir in juice. Keep warm.
Place salmon on a baking sheet coated with cooking spray; sprinkle salmon with remaining 1/4 teaspoon salt, 1/4 teaspoon black pepper, and 1/8 teaspoon red pepper. Bake salmon at 400 degrees fro 8-10 minutes or until fish flakes easily when tested with a fork. Place one filet on each of 4 plates; top with leek mixture.