Preheat oven to 425°F (220°C). Scrub the russet potatoes under running water to remove dirt; pat dry with a towel. Prick each potato 6–8 times all over with a fork to allow steam to escape.

Oil and season

Rub each potato all over with the olive oil so skin is lightly coated. Sprinkle the coarse salt and 1/2 tsp freshly ground black pepper over the potatoes and rub gently so they adhere to the skin.

Bake

Place potatoes directly on the oven rack or on a baking sheet lined with foil. Bake at 425°F (220°C) for 45–60 minutes, until skins are crisp and a paring knife or skewer slides easily into the center (time depends on potato size). If baking several at once, rotate the pan once halfway through for even cooking.

Prepare toppings

Prepare green onions and cheese

While potatoes bake, rinse and trim the green onions. Thinly slice both the white and green parts (about 3 green onions yields ~1/3 cup sliced). Shred the cheddar cheese if not pre-shredded and keep covered in the refrigerator until ready to use.

Portion butter and sour cream

Measure the butter into four equal portions (1 tablespoon each) so it's ready to top hot potatoes. Spoon the sour cream into a small bowl and stir briefly to loosen; you will use approximately 1/4 cup per potato.

Assemble potatoes

Split and fluff

When potatoes are done, remove from oven using oven mitts. Place on a heatproof surface. Using a sharp knife, make a lengthwise slit about 3/4 of the way through each potato. Press the ends gently toward each other to open the potato and fluff the interior with a fork to create space for toppings.

Add butter and season

Place 1 tablespoon of unsalted butter into the hot center of each split potato so it melts into the fluffy flesh. Season lightly with the optional 1/4 tsp salt and 1/4 tsp black pepper across all potatoes, or to taste.

Top with sour cream, cheese, and green onions

Spoon about 1/4 cup sour cream onto each potato, sprinkle approximately 1/4 cup shredded cheddar over the sour cream so it starts to melt from the residual heat, then scatter sliced green onions on top. If you prefer the cheese more melted, return topped potatoes to the oven for 2–3 minutes or use a microwave for 20–30 seconds.

Serve

Serve each baked potato hot, with additional salt and pepper available at the table. Leftover toppings may be refrigerated for up to 3 days.