Vegetarian Ricotta Spinach Meatballs

• 1 cup ricotta
• 2 eggs
• 1 red onion, finely chopped
• 1 cup parmesan cheese
• 100 g frozen spinach, thawed
• 0.75 cup bread crumbs
• 700 g passata
• 2 garlic cloves, crushed
• 2 tsp oregano
• 2 tbsp balsamic vinegar
• 400 g wholemeal pasta