Peel the tomatoes: place them in a heatproof bowl, add boiling water to cover and leave for 1 minute. Lift out with a slotted spoon and plunge into a bowl of cold water. Leave for 1 minute, then drain. Slip the skins off the tomatoes and chop the flesh.

Heat half the oil in a frying pan and fry the onion with the garlic and cumin seeds for 5 minutes, until the onion softens. Add the chilies and tomatoes, then stir in the tomato paste. Crumble the bouillon cube over, stir well and cook gently for 5 minutes, until the chili is soft but the tomato has not completely broken down. Stir in the corn and fresh cilantro and heat gently to warm through. Keep warm.

Sprinkle grated cheese in the middle of each tortilla. Spoon some tomato mixture over the cheese. Fold over one edge of the tortilla then the sides and finally the remaining edge, to enclose the filling completely.

Heat the remaining oil in a separate frying pan and fry the filled tortillas for 1 - 2 minutes on each side until golden and crisp. Serve with cilantro, shredded lettuce and sour cream.