Prepare the greens: Place spinach and arugula in a large salad bowl.
Slice the apples: Core and slice apples thinly; drizzle with a little lemon juice to prevent browning.
Toast the walnuts: In a small skillet over medium heat, toast walnuts for 3–4 minutes until fragrant. Let them cool.
Assemble the salad: Add apples, cranberries, walnuts, and feta to the greens.
Make the dressing: In a jar, combine olive oil, apple cider vinegar, honey, Dijon, salt, and pepper. Shake or whisk until blended.
Toss and serve: Drizzle dressing over the salad just before serving. Toss lightly to coat everything evenly.
