01 - Heat vegetable oil in a large skillet over medium heat until shimmering.
02 - Add the chopped onion and sauté for 3 to 4 minutes until soft and translucent.
03 - Stir in the minced garlic and chopped chiles. Cook for 2 minutes until fragrant.
04 - Add the diced tomatoes and cook, stirring frequently, for 5 minutes until they soften and release their juices.
05 - Add the cubed potatoes, ground cumin, salt, and black pepper. Stir thoroughly to coat all ingredients evenly in the sauce.
06 - Pour in 3/4 cup water, just enough to partially cover the potatoes. Bring to a simmer, then cover the skillet.
07 - Cook covered for 15 to 20 minutes, stirring occasionally, until the potatoes are fork-tender and the sauce has thickened.
08 - Taste and adjust seasoning as needed. Garnish with fresh cilantro if desired. Serve hot with warm tortillas or use as a taco filling.