Core the peppers and finely dice the flesh along with the celery. Set aside.
Heat the oil in a large saucepan on a medium heat. Tip in the diced onion and sauté for 2-3 minutes until softened. Add the garlic, peppers, celery and spring onions and cook gently for a further five minutes.
Increase the heat to high, add in the spices and cook, stirring continuously, for 1 minute.
Add the tinned tomatoes, sun-dried tomatoes, vegetable stock, lemon zest salt and pepper. Bring to boil, reduce the heat and simmer, uncovered, for 10-15 minutes.
Taste the soup and adjust the seasoning if necessary.
Ladle into warmed bowls and sprinkle over a little extra sumac and plenty of freshly ground black pepper.
