Mix masa harina, warm water, and salt until a soft dough forms
Let the dough rest for a few minutes
Prepare fillings such as refried beans, cheese, or cooked pork
Divide the dough into equal balls
Flatten one ball into a thick disc
Add filling to the center
Fold the dough around the filling and seal it
Gently flatten the stuffed ball into a thick patty
Repeat with the remaining dough and filling
Heat a skillet or griddle over medium heat
Cook each pupusa for a few minutes per side until golden and cooked through
Serve warm with curtido and salsa roja