In a small bowl, whisk together the olive oil, lemon juice, honey, and dijon mustard until emulsified and slightly thickened. Season with salt and pepper to taste.
In a large bowl, toss the spinach and onion slices in the vinaigrette until everything is well coated.
Place half of the spinach onion blend into the serving dish. Scatter half of the nectarine slices, mozzarella balls, and cucumber wedges over the spinach. Top with remaining spinach blend and garnish with the last of the toppings. Serve immediately.
Optional and not pictured: Add ⅓ cup whole or sliced almonds.
If not serving immediately, prep all of your ingredients but do not dress the salad until service.