In a large bowl, combine cabbage, onion, and carrots. Pour the boiling water over the vegetables and toss. Let sit 10 minutes, then drain. Combine vinegar, oregano, and salt. Pour over the slaw and toss to coat. Chill at least 20 minutes, or overnight for best results.

Add tomatoes, garlic, onion, jalapeños, oregano, and salt to a food processor. Process until smooth. Transfer to a skillet over medium heat and cook 5-6 minutes until some liquid reduces. Set aside.

In a large bowl, combine masa flour, warm water, salt, and oil. Knead until smooth and pliable, about 2 minutes. The dough should feel like soft Play-Doh. Cover with a damp towel.

In a pot, combine pork, achiote paste, tomatoes, onion, garlic, salt, pepper, and water. Bring to a boil, reduce heat, and simmer covered for 45 minutes until tender. Shred the pork and mix back into the reduced sauce.

Take a golf ball-sized piece of dough and flatten it in your palm into a disc. Add a spoonful of pork and cheese in the center. Fold the edges up and over the filling, seal, and gently flatten into a thick disc about ¼ inch thick.

Heat a lightly oiled griddle or skillet over medium heat. Cook pupusas 3-4 minutes per side until golden brown with light charring.

Serve hot with curtido and salsa on the side.