Preheat the oven to 200°C / gas mark 6, slipping in a baking tray at the same time.
To make the sauce, heat the oil in a pan on the stove and fry the onion, pepper and chilli. Add the salt and cook gently for 15 minutes and, once soft, add the chopped coriander stalks.
Add the canned tomatoes, then swill the cans out with water and add this too. Spoon in the ketchup and let things come to a simmer, leaving the sauce (or salsa, in keeping with the Mexican mojo) to cook while you get on with preparing the filling - about ten minutes.
To make the filling, mix the drained beans and sweetcorn in a bowl. Add most of the grated cheese, reserving some to sprinkle on the top at the end, and mix together.
Start to assemble the lasagne by spooning about a third of the salsa into the bottom of your ovenproof dish and smearing it about, then layer on two tortillas so that they cover the sauce overlapping slightly, like a Venn diagram.
Add a third of the beans and cheese mixture, covering the tortillas, and then about a quarter of the remaining salsa and another two tortillas.
Repeat with another third of beans and cheese, and some more salsa before layering on another two tortillas. Finally, add the last layer of beans and cheese, nearly all of the remaining salsa and cover with the last two tortillas. Spread the very last bit of salsa over the tortillas and sprinkle with the remaining cheese.
Bake in the oven for 30 minutes, and let it rest for a good 10-15 minutes before slicing like a pizza, and eat with some avocado salsa.
Recipe from Nigella: Kitchen by Nigella Lawson (published by Chatto & Windus).