Start by preheating your oven to 400°F (200°C). Wash the russet potatoes thoroughly and scrub the skins. Dry them, then rub each potato with olive oil and sprinkle with a pinch of salt. Pierce each one several times with a fork to allow steam to escape during baking. Place them directly on the oven rack or a baking tray and bake for 45 to 60 minutes until soft inside and crispy outside.
While the potatoes are baking, heat olive oil in a skillet over medium heat. Add the diced onion and garlic, cooking until they’re soft and fragrant. Then, stir in the black beans, corn, taco seasoning, and water. Let everything simmer for about 5–7 minutes until the mixture thickens and is heated through. Taste and adjust seasoning if needed.
Once the potatoes are done baking, remove them from the oven and let them cool slightly. Carefully slice each one open lengthwise and fluff the insides with a fork. Spoon a generous amount of taco filling into each potato. Sprinkle shredded cheddar cheese on top and let it melt from the heat. Finish by adding salsa or tomatoes, lettuce, sour cream, avocado, chopped cilantro, and a fresh squeeze of lime.