Preheat a nonstick skillet over medium-high heat. Butter the two slices of bread, season one side with sea salt and place that slice butter-side down in the hot pan. Place slices of BelGioioso Fontina on the bread and top with the other bread slice, buttered side up. Season top side with sea salt and grill on both sides for 4 to 5 minutes or until golden brown and cheese is melted. Slice and serve immediately.