To cook the pork, add to a large pot and cover with the water ¾ of the pot.
Add a pinch of salt, garlic and onion. Bring to the boil and reduce heat. Simmer for 1 hour.
Strain the pork and place in a bowl reserving the broth.
To make the peanut sauce place peanuts, tomatoes, sesame seeds, salt and pepper into a blender and grind to a paste. You may need to scrape the sides with a plastic spatula once or twice so that all the ingredients are combined well.
Add the sauce and the pork to a frypan and cook for 15 minutes.
Heat tortillas in the oven for 1–2 minutes. Alternatively, heat a frypan and add the tortillas, one at a time. Cook for 1–2 minutes each side. Keep warm while you heat the rest of the tortillas.
Serve the pork with peanut sauce on the hot corn tortillas.