Chop the spring onions into rounds. Heat 2 tbsp of the oil in a large lidded saucepan. Add the garlic and the green part of the onions and cook until softened but not coloured. Add the tinned tomatoes, some sea salt, a pinch of sugar, the saffron (if using), paprika and balsamic vinegar. Simmer for 5 minutes, then pour into a separate bowl and wipe the pan clean.