Preheat oven to 400°F (200°C).
In a 12-inch oven-safe cast iron skillet, toss the diced potatoes with olive oil, salt, black pepper, and garlic powder until evenly coated.
Spread potatoes in a single layer and roast in the oven for 25 to 30 minutes, or until golden brown and tender, tossing halfway through.
While potatoes roast, brown the ground beef and diced onion in a separate skillet over medium-high heat until the meat is fully cooked. Drain any excess grease.
Stir smoked paprika and dried oregano into the beef mixture.
Remove the potato skillet from the oven. Layer the seasoned beef mixture over the potatoes.
Top the beef and potatoes with shredded sharp cheddar cheese.
Return the skillet to the oven for 5 to 7 minutes until the cheese is completely melted and bubbly.
Garnish with chopped parsley and serve immediately.