Onion & Mozzarella Salad

1/2c sliced red onion
1 small lemon
1qt chopped romain lettuce
2c baby arugula
1c halved cherry tomatoes
4 sliced basil leaves
1/2c fresh mozzarella, cubed
2 tbs balsamic vinegar
2 tbs olive oil
salt & pepper

Soak onion slices in lemon in a small bowl. Combine lettuce, arugula, tomatoes, and mozzarella in a large bowl. Add onions. Sprinkle with vinegar, oil, basil, salt, and pepper and toss before serving.