Optional: Let the red onion soak in an ice water bath for 10 minutes, then squeeze dry with paper towels.
In a large serving bowl add the spinach, thinly sliced apples, red onion, toasted pecans, feta cheese and cranberries.
To a mason jar with a tight fitting lid, add the vegetable oil, apple cider vinegar, maple syrup, mustard, garlic powder, salt and pepper. Shake well to combine.
Pour the dressing over the salad and toss to combine.
Notes
See above notes to prep salad up to 8 hours ahead of time.