In a small bowl, whisk together the honey and soy sauce. Pour into a resealable plastic bag and add the garlic and salmon filets. Seal the bag and turn over a few times to coat the fish in the marinade. Place in the refrigerator and allow to marinade for 45-60 minutes. (Note: I recommend placing the bag in a bowl as a precaution against leaks).
Preheat the oven to 425 degrees F. Remove the fish from the marinade. Place on a lightly greased baking sheet. Pour the remaining marinade into a small saucepan.
Bake the fish for 8-10 minutes, or until just barely cooked through (it’s better to undercook salmon than overcook it).
While the fish is cooking, bring the marinade to a simmer over medium-low heat and allow it to reduce and thicken into a glaze.
Heat a skillet (preferably nonstick) over medium-high heat and add the butter. If using, sprinkle the brown sugar over the pineapple slices (it will help caramelize and enhance the sweetness). When the butter begins to bubble in the pan, add the pineapple slices. Once they’ve caramelized on one side, use tongs or a spatula to flip the slices and brown on the other side. Remove from the heat.
Brush the marinade on the salmon before serving. Top each filet with a slice of caramelized pineapple.