Add water into a large saucepan, and place in the meat, the peppercorns, salt and a quarter of a medium onion and bring to a boil. Once boiling, lower the heat, cover and simmer for approximately 1 ½ hours or until the meat becomes very tender.
Turn off the heat and allow to cool. Drain the meat, reserving 1/3 cup of the broth.
Crush the garlic into a cup and stir vigorously with 1/4 teaspoon of salt until it thickens into a paste.
Heat some cooking oil in a large skillet and add in the chopped onion and garlic paste and cook until the onion has softened and become translucent.
Slice the chili intro short strips and add them along with the tomatoes into the pan. Sauté everything for 3-4 minutes.
Add the cooked meat, cumin and some freshly ground pepper to taste.
Continue cooking until the meat is hot throughout then stir in the reserved broth and season with more salt if necessary.
Serve warm as a main dish or tacos or other tortilla dishes.