Line the bottom of a pressure cooker with the banana leaf, making sure to cover it completely and leave extra on the sides to fold over the meat. Add the pork, cut into pieces.

In a blender, combine the 2 bars of achiote paste, garlic cloves, and the juice of the sour oranges. If the oranges aren't very tart, add the juice of 3 limes.

Add salt and blend until the achiote paste is fully dissolved. Pour this mixture over the meat.

Fold the extra banana leaf over the meat. Once the pressure cooker starts to whistle, cook for 30 minutes. Check to make sure it doesn't dry out, so the leaf doesn't stick and the meat doesn't burn.

Remove the banana leaves and it's ready!

For the salsa: Remove the stems and seeds from the chiles, and finely chop the red onion.

Place them in a pot, add oregano and salt to taste, and cover with white vinegar. Cook over medium heat. Once it boils, cook for 5 minutes and it's ready!

Serve with corn tortillas and the salsa!