Finely chop ½ medium red onion and add to a large bowl. Whisk in ⅓ cup vegetable oil, ¼ cup apple cider vinegar, 2 tablespoons maple syrup, 4 teaspoons Dijon mustard, and ½ teaspoon kosher salt. Let sit for at least 10 minutes for the flavors to meld. Meanwhile, prepare the cabbage.
Cut 1 small green cabbage into 8 wedges through the core, then cut the core from each piece. Thinly slice the cabbage wedges crosswise to shred (about 10 cups). Pick the leaves from 1 bunch fresh parsley and coarsely chop until you have ⅔ cup.
Add the shredded cabbage, chopped fresh parsley leaves, ¾ cup toasted, sliced almonds, and ¾ cup dried cranberries to the dressing. Toss to combine. Taste and season with kosher salt and black pepper as needed.
