Preheat your oven to 400°F (200°C). Poke each potato multiple times with a fork, then place them directly on the oven rack. Bake for about 45-60 minutes, or until they are tender and easily pierced with a fork.
While the potatoes bake, heat olive oil in a large skillet over medium heat. Add the diced onion and sauté until it becomes translucent, about 4-5 minutes.
Add the ground beef or turkey to the skillet and cook until browned, breaking it up with a spoon (about 6-8 minutes). Drain excess fat if needed.
Stir in the taco seasoning, black beans, and corn. Cook for an additional 3-4 minutes, allowing the mixture to heat through. Adjust seasonings with salt and pepper to taste.
Once the potatoes are done baking, remove them from the oven and let cool slightly. Carefully cut them open lengthwise and fluff the insides with a fork.
Spoon the cheesy taco beef mixture generously into each potato. Top with shredded cheddar cheese and return them to the oven for an additional 5-7 minutes, or until the cheese has melted and is bubbly.
Remove from the oven and let cool for a couple of minutes before serving. Drizzle sour cream over the top if desired and garnish with chopped cilantro.