Boil the water in a large pot and add the tablespoon of salt and tablespoon of vinegar. Simmer the potatoes for about 5 minutes, or until they’re losing their crispness but are still firm. Drain and cool.
Heat a cast iron pan and add the oil. When the oil is hot, add the onion and bell pepper. Let them soften and cook until the onion is translucent. Add the potatoes, increasing the oil slightly if using Russet potatoes.
Stir every so often, ensuring nothing gets too dark as it cooks. Add in the cubed corned beef so it can get some color and warm up. Wait until the potatoes are nearly cooked before adding the meat so it doesn’t cook too long and become mushy. Season with salt and pepper to taste before serving.