Cut the onion into small cubes and add to a frying pan with the extra-virgin olive oil. Gently fry, and when it starts to turn golden brown, add the cubed peppers and corn.
Once all the vegetables are golden brown, add the garlic, chilli and grated tomatoes. Add salt and pepper and cook for 10 minutes over a medium heat.
Take off the heat and put by. Wipe the frying pan with kitchen paper so that you can begin to assemble the tortillas. Add a tortilla to the frying pan and leave to warm for a minute, before adding the filling and folding up the burrito tightly.
Cook the burrito until both sides are nicely toasted. Top off with the green chilli sauce.