How to Make It
Combine 1 cup julienne-cut red bell pepper, 1 cup sliced red onion, 2 tablespoons olive oil, and 1 tablespoon balsamic vinegar in a large bowl; let stand 15 minutes. Add 6 cups baby spinach, 1/4 teaspoon salt, and 1/4 teaspoon black pepper. Toss. Top with 6 tablespoons finely chopped fresh mozzarella.