I have lost the rachel allen recipes for the aztec tortilla soup, now I am so stuck in perfecting it that I really need your help if at all I want to bring it to the table from the kitchen. Can you tell me whether adding some brown onion in the aztec tortilla soup recipe is advisable? Will the soup turn too sweet, if it does then how can I cut its sweetness? Once I have put the garlic, tomatoes and the onion on a flat cast-iron griddle on medium heat, do I need to turn them every other minute and let them get dark in the spots? Can you teach me how to make the aztec tortilla soup properly?