One-Pot Vegan Meatball Spaghetti Bake

Name: One-Pot Vegan Meatball Spaghetti Bake
Prep time: 10 min
Cook time: 35 min
Total time: 45 min
Cuisine: European, Italian, Mediterranean
Ingredients: 600g (21 oz) vegan meatballs; 2 red onions, halved and sliced; 1 red pepper, deseeded, sliced and cut into chunks; 1 tbsp olive oil; 1 tsp dried oregano; 1 tsp garlic powder; a good grinding of salt and pepper; 400g (14 oz) spaghetti, broken in half; 2 x 400g (14 oz) tins chopped tomatoes; 800ml (3 1/3 cups) vegetable stock (I made up a litre/4 1/4 cups, so I had some reserved if I needed it); 4 tbsp tomato puree; 1 tbsp balsamic vinegar