Step 1

Heat the oil in a large ovenproof frying pan over medium heat. Add onion and cook, stirring, for 3 mins or until softened. Add the meatballs and cook, turning occasionally, for 5 mins or until meatballs are browned all over.

Step 2

Add the passata and cook, stirring occasionally, for 5 mins or until the meatballs are cooked through. Remove from heat. Stir in the spinach. Arrange the mozzarella over the passata mixture.

Step 3

Preheat grill on high. Place the frying pan under grill and cook for 3 mins or until the mozzarella melts and is golden brown.