Chorizo and Potato Empanadas

For the dough:

all-purpose flour, plus more for kneading

masa harina (corn tortilla flour)

baking powder

salt

vegetable oil

warm water

For the filling:

large boiled potato, peeled and cut into 1/2-inch cubes

generous cup of chorizo

small yellow onion, chopped

sliced pimento-stuffed green olives

golden raisins

dried whole oregano (preferably Mexican)

Salt and freshly ground black pepper

egg beaten with 1 tablespoon water

For the roasted tomato and chile de árbol salsa:

plum tomatoes (about 4)

to 6 chiles de árbol, depending on how spicy you like it

olive oil

medium white onion, chopped

garlic cloves, crushed

chopped fresh cilantro

salt

freshly ground black pepper