• Heat the oil, onion & garlic in a large frying pan over medium-high heat. Cook, stirring occasionally, for 5 minutes or until onion is softened. Add spinach & stir for 1 minute or until spinach is just wilted; remove from the heat; let cool for 5 minutes.
• Combine the spinach mixture, turkey, parmesan, breadcrumbs, parsley, egg, salt & pepper. Mix thoroughly until well combined – the easiest way is to use your hands & really squeeze all the ingredients together.  
• Preheat oven to 375°F (190°C). Line a baking sheet with parchment. Drop 2 tablespoons each of the mixture onto the baking sheet; roll into balls. Lightly wet your hands or use surgical gloves to prevent the mixture sticking to your hands. Just note, the mixture is quite a wet mixture. Spray the balls with cooking spray & bake for 30 to 35 minutes, turning once during cooking, until meatballs are golden & thoroughly cooked – a thermometer when inserted into a meatball reaches 165°F. 

To make the sauce:

• While the meatballs are cooking, wipe the frying pan out. Heat the oil over medium-high heat. Add onion & cook for 5 minutes, stirring occasionally, until onion is softened. Add garlic & cook 1 to 2 minutes until garlic is fragrant. Add tomato paste & wine. Cook, stirring occasionally, until the wine is reduce by about half. Add red pepper, tomatoes with their juice, sugar, salt & pepper. Break the tomatoes into chunks using the side of a spoon. Bring the sauce to a boil then reduce the heat to medium. Simmer, uncovered, stirring occasionally, for 10 minutes or until sauce is thickened. 
• Place meatballs into sauce & top each with some mozzarella. Place under hot broiler, about 6 inches from heat source, for 1 to 2 minutes or until cheese is melted.