In a large skillet, heat 1 tablespoon of olive oil over medium heat. Add the diced russet potatoes and season with salt and pepper. Cook until they are golden brown and tender, about 10-12 minutes. Stir occasionally to ensure even cooking. Once done, remove them from the skillet and set aside.
In the same skillet, add the remaining tablespoon of olive oil. Increase the heat to medium-high and add the thinly sliced beef sirloin or flank steak. Season with salt, pepper, and ground cumin. Sauté for about 5-7 minutes until the beef is browned and cooked through. Remove the beef from the skillet and set aside.
Add the sliced onion and minced garlic to the skillet. Sauté for about 3-4 minutes until the onion becomes translucent. Next, add the sliced jalapeños and chopped Roma tomatoes, cooking for an additional 3-4 minutes until the tomatoes soften.
Return the cooked beef to the skillet and stir in the tomato sauce, dried oregano, and the cooked potatoes. Mix well to combine all the ingredients and let it simmer for about 5 minutes, allowing the flavors to meld together. Taste and adjust seasoning with salt and pepper if needed.
Plate your delicious Bistec Ranchero and garnish with freshly chopped cilantro. Serve with warm tortillas or over a bed of rice to soak up the flavorful sauce.
