Don't overcook the spinach.
Pour the balsamic vinegar and honey into a small saucepan; then bring to a boil. Cook over medium heat until the volume is reduced by half and a syrupy consistency is obtained, 5-7 minutes. Set aside. Prepare the spinach. Wash and drain rapidly then transfer to a saucepan without adding any water. The water trapped in the leaves after gentle shaking is enough to cook them. Add salt, cover and cook over high heat 3-4 minutes until the leaves wilt. Avoid overcooking, otherwise the spinach will become brownish. Transfer the spinach to a colander and press to remove excess water. Set aside. Lightly oil salmon on both sides. Heat a grooved, thick-bottom frying pan or a skillet that has been sprayed with cooking spray. When hot, add the fish, skin side down, and cook until the edges become opaque and lighter colored, about 5 minutes. Turn and cook an additional 3 minutes. Peel off the skin then season with salt and pepper. Check with a fork to see if it is cooked through. Transfer the spinach to warmed serving plate. Place the fish on top and drizzle with the balsamic syrup. Serve. Have a small cup of mandarin oranges for dessert.