Heat a large skillet over medium-high heat. Add 2 tablespoons of oil and add the liver strips, working in batches if necessary. Cook for about 2 minutes or until browned on both sides. Season with salt and pepper to taste. Remove liver from skillet and set aside on a plate.

Add the remaining oil to the same skillet. Add the onions, tomatoes, garlic and cumin. Sauté until the vegetables are soft. Add the liver back to the skillet and cook for 2 minutes more until liver reaches an internal temperature of 160°F. Sprinkle with fresh parsley or cilantro and serve the liver on top of an arepa.