Heat the oil in a small pan. Add the onion and cook for 2 minutes. Tip in the chopped tomatoes, pomodorino tomatoes, olives and 100ml water. Simmer for 5-8 minutes.
Meanwhile, cook the gnocchi according to the instructions on the packet, adding the spinach for the last 30 seconds of cooking time.
Drain the gnocchi and spinach, then add to the pan of tomato sauce. Stir in half the basil, then divide between bowls. Crumble the Greek-style salad cheese over the top and garnish with the remaining basil.