Heat butter in skillet set over medium heat; cook onions for about 8 minutes or until softened. Add apple, salt and pepper; cook for 3 to 5 minutes or until apple is tender-crisp.
Increase heat to medium-high; cook for about 10 minutes or until onions and apple are golden and caramelized. Stir in 1/4 cup Ken’s® Lite Raspberry Walnut; remove from heat.
Meanwhile, preheat oven to 350°F. Place Brie cheese on baking sheet lined with parchment paper. Spoon onion mixture on top of Brie; sprinkle with walnuts and drizzle with remaining Ken’s® Lite Raspberry Walnut Vinaigrette. Bake for about 10 minutes or until cheese is softened.