Melt butter with horseradish, syrup, vinegar, salt, and pepper in a small sauce pan over medium heat. Bring to a boil and allow to reduce by a third. Cool completely.
For the salmon...
Preheat the oven to 400 degrees.
Place salmon fillets in a baking dish. Pour glaze over salmon fillet(s) and allow to marinate one hour at room temperature.
Bake for 17 - 20 minutes, or to desired degree of doneness.