Place kale pieces and ½ cup apple cider vinegar in a pan, and marinate for 20 minutes.
Preheat oven to 400°. Place salmon on foil-lined sheet pan, brush with 1/4 cup maple syrup and bake for about 15 minutes, until salmon is flaky. Set aside to cool; then flake with a fork.
In a large bowl, toss kale in remaining maple syrup and apple cider vinegar. Add remaining ingredients, and toss. Season with salt and pepper to taste. Garnish with red pepper flakes.
Can be refrigerated and kept for 3–4 days.