Put the tomatoes, garlic, onions, orange zest, herbs, saffron, stock and sugar into a pan and bring to a boil. Cover, reduce the heat and simmer for 20 minutes.
Discard the herbs and zest, then purée the broth in a mixie.
Return the purée to the pan and stir in the oil, vermicelli, and salt and pepper to taste. Bring to another boil then simmer, uncovered, for 8-10 minutes, stirring occasionally, until the pasta is cooked and the broth has thickened. Season to taste and serve, garnished with basil.