Dry-fry the minced beef and onion in a medium pan for about 5 minutes until browned. Add the garlic and fry for 1 minute, then add the tomatoes, tomato purée, oregano, cumin, and season.
Slice and deseed the chilli. Reserve a few slices for garnish, then finely chop the remainder and add to the minced beef. Bring the pan to the boil, then cover and simmer for 15 minutes.
Spread a little mince in the centre of each tortilla, roll up and place in a baking dish. Top with the grated cheese, chilli and jalapeño peppers and bake for 10 minutes until golden. Serve with extra jalapeños and guacamole.