In a medium pan, over medium heat, brown the onions. Add the red pepper and cook for 4 minutes until red pepper starts to soften.
Add 400 ml water to the pan, stir in the contents of the pouch and bring to the boil while stirring. Add the beans, cumin, coriander and chilli flakes.
Reduce heat and simmer uncovered for 15 minutes.
Place the nachos in an ovenproof dish and drizzle the sauce over. Sprinkle the cheese over and bake in the oven for 10 minutes until the cheese has melted. Serve with guacamole.