Preheat your oven to 400°F (200°C). Pierce the potatoes several times with a fork and rub them lightly with olive oil. Place them directly on the oven rack and bake for 50 to 60 minutes, or until the insides are tender when poked with a knife.
While the potatoes are baking, place a skillet over medium-high heat. Add the ground beef and cook until browned, breaking it into small crumbles with a spatula. Drain any excess grease. Season the beef with salt, pepper, and garlic powder, then set aside.
Once the potatoes are cool enough to handle, cut them in half lengthwise. Use a spoon to scoop out the flesh, leaving about a 1/4-inch thick shell of potato against the skin. Save the scooped-out potato for mashed potatoes later!
Increase the oven heat to 425°F (220°C). Brush the inside and outside of the potato shells with a little more olive oil and sprinkle with a pinch of salt. Place them hollow-side down on a baking sheet and bake for 5 minutes. Flip them over and bake for another 5 minutes until the edges are crispy.
Fill each crispy potato shell with a generous amount of the seasoned ground beef. Top each one with plenty of shredded cheddar cheese. Return the tray to the oven for 3 to 5 minutes, or until the cheese is bubbly and melted.
Remove the potato skins from the oven. Top each one with a dollop of sour cream and a sprinkle of fresh green onions before serving warm.