Preheat the oven to 200C / 180C fan / Gas Mark 6.
Mix the baked beans, chopped tomatoes, onion, cumin and chilli powder together in a bowl.
Spread a spoonful of the bean mixture on the bottom of an ovenproof dish.
Lay one tortilla on top and spread with a third of the remaining bean mixture.
Sprinkle with a handful of grated cheese.
Repeat with two more layers of tortilla, bean mixture and cheese.
Top with the final tortilla, the last of the cheese and any remaining bean mixture.
Bake for 15-20 minutes until the cheese is golden and bubbling.
Scatter with coriander if using, then slice into quarters and serve.