01 - Combine spinach, strawberries, red onion, feta cheese, nuts, and cucumber (if using) in a large salad bowl.
02 - Whisk together olive oil, balsamic vinegar, Dijon mustard, honey, salt, and pepper in a small bowl or jar until fully emulsified.
03 - Drizzle vinaigrette over salad immediately before serving. Toss gently to coat all ingredients evenly.