Heat a skillet equipped with a lid over a medium heat and cook the onion in some cooking fat until soft, about 5 minutes.
1 onion, Cooking fat
Stir in the pork tenderloin cubes and continue cooking for about 8 minutes, until browned.
½ lb pork tenderloin
Now add the kidney pieces and cook for a further 5 minutes while stirring frequently.
4 lamb kidneys
Add the tomatoes and oregano, season to taste with sea salt and freshly ground black pepper and bring to a boil.
1 can, ½ teaspoon dried oregano, Sea salt and freshly ground black pepper to taste
Reduce to a simmer, cover, and cook for 10 minutes.
Uncover and cook for another 5 minutes.
Adjust the seasoning if needed and serve.