Preheat the oven to 400°F. Wash the potatoes and pat them dry. Use a fork to poke holes on all sides. Then, rub the potatoes with olive oil and a sprinkle of salt.
Place the potatoes on a baking sheet and bake for 45 to 60 minutes, flipping them over about half way through cooking. They’re done when easily pierced with a fork all the way through the middle. Leaving the oven on, set them aside to cool a bit.
While the potatoes are in the oven, add a tsp of oil in a large skillet over medium-high heat. Add the diced onions and 1/4 teaspoon salt. Cook, stirring every minute or so, until the onions are browned. Add the ground beef and sprinkle with another 1/4 teaspoon salt and garlic powder. Cook, breaking up the ground beef into crumbles. Cook until browned, gradually mixing in with the onions, then remove from heat.
Once they're cool enough to handle, cut each potato in half. Then use a spoon to scoop out the insides of the potato and place in a large bowl, leaving about 1/4 inch in the potato shell. Add about 1 cup of cheese, the sour cream or mayo, greek yogurt, pepper, and the remaining 1/2 teaspoon salt. Stir in the cooked onions and ground beef. Taste and add more sour cream if you’d like a creamier filling, add more salt, etc. Make these to your liking!!
Arrange the empty potato halves on the baking sheet like boats. Stuff the halves with the filling (they'll be stuffed pretty high!). Then, return the potatoes to the oven and bake for 10 minutes. Sprinkle the tops with the remaining cheese and bake for another 3 to 5 minutes, until the cheese has melted.
When ready to serve, top with all your favorite toppings (shredded lettuce, tomatoes, diced pickles, etc.) and drizzle over your favorite burger sauce!