Salvadoran
For the curtido, pour boiling water over the cabbage, drain after 1 minute and mix with the carrot, onion, vinegar, oregano and 1 tsp of the salt; refrigerate for at least 1 hour.
For the salsa, simmer the tomatoes in water for 5 minutes, peel, blend with 0.5 tsp of the salt and simmer the puree for 10 minutes until slightly thickened.
Mix the masa harina with 1 tsp of the salt and the warm water and knead for 2-3 minutes into a soft dough that does not crack; divide it into 12 balls.
Mash the beans and cheese together into a thick paste.
With oiled hands, flatten a ball into a 10 cm cup, put in a twelfth of the filling (about 45 g), close the dough over it and pat it into a 12 cm disk about 1 cm thick.
Cook the pupusas on a lightly oiled griddle or heavy pan over medium-high heat for 4-5 minutes per side until browned in spots and the cheese is melted.
Serve hot, 2 per plate, with the curtido and tomato salsa on top.