Preheat your oven to 375°F (190°C).
In a large mixing bowl, combine the diced potatoes, smoked sausage, sour cream, ranch dressing, garlic powder, onion powder, black pepper, and salt.
Transfer the potato mixture into a greased 9x13-inch baking dish.
Top the mixture with shredded cheddar and grated parmesan cheese.
Cover the dish with aluminum foil and bake for 30 minutes.
Remove the foil and bake for an additional 15-20 minutes, or until the top is bubbly and golden brown.
Once done, remove the bake from the oven and let it cool for a few minutes.
Garnish with chopped green onions before serving.