Slice stem end from Kalettes, allowing some leaves to fall loose and leaving center leaves intact. In salad bowl, add Kalettes and drizzle with vinegar. Sprinkle with 1/8 teaspoon salt and toss to coat. Set aside for 10 minutes.
Cook sliced onion to pan and saute over medium high heat until caramelized, about 10-15 minutes. Let cool.
In a measuring cup, add extra virgin olive oil, apple cider vinegar, 1/8 teaspoon salt and pepper to taste. Shake or stir to combine dressing. Add the sliced apple, almonds, and onions to bowl with Kalettes. Pour the dressing over the salad and toss to coat.