In a large bowl, combine thinly sliced cabbage, grated carrot, and Mexican oregano.

In a measuring cup, mix together hot water, apple cider vinegar, kosher salt, and sugar until dissolved. Pour over cabbage and carrot, tossing to coat. Let sit for about 30 minutes, then refrigerate for at least 4 hours or overnight.

Combine masa harina and a pinch of salt in a mixing bowl. Gradually add cold water, stirring until a soft, non-sticky dough forms. Cover with a damp cloth.

Divide the dough into equal portions, flatten each into a disc, and add filling to the center. Fold edges over filling and pinch to seal.

Preheat a skillet over medium heat. Grease lightly with oil. Cook each pupusa for about 4-6 minutes on each side until golden brown.

Serve the pupusas alongside the curtido, with lime wedges and salsa for added flavor.