Slice the tomatoes and mozzarella and arrange in a spiral in a dish or bowl.
Drizzle with olive oil, balsamic vinegar and a sprinkle of salt and pepper.
Top with pistachios and basil and serve immediately.
If you wish to make the salad ahead just arrange the tomatoes and cheese and cover with plastic wrap in the fridge. Chop the pistachios and set aside. When you're ready to serve, dress the salad and add fresh basil.