Place the corn in a pan and let it cook (if it's raw) and the liquid will evaporate. Then leave it still on high heat so it blackens a bit. After 1-2 minutes stir and repeat until it looks nicely charred. You don't need to add oil for this.
Mix the tomato, corn and lettuce. Add salt and pepper to taste
To assemble the burrito, add cheese on the tortilla at the centre, forming a line and leaving 4cm/1.5in without filling on the top and bottom so that you can close it later. On top of the cheese add the beef, beans, peppers, corn, tomato and lettuce.
To close the burritos first fold the top and bottom of the tortilla we left uncovers onto the filling. Then roll it from one side to the other, keeping those edges tucked in.
Toast your burrito on a preheated pan or grill over medium-high heat. Alternatively, you can also heat them up in the oven.