Preheat oven to 375. Rub outside of potatoes with the oil. Bake for 50 minutes, or until softened. Slice horizontally and scoop out flesh of potatoes.

Place the flesh in a bowl and mash. Maintain oven temperature.

Meanwhile, cook beef in a heavy skillet over medium heat until browned. Add tomatoes, scallions, mashed potatoes, salt and pepper to taste. Cook 1 minute.

Scoop mixture into potato shells. Sprinkle evenly with cheese. Place on baking sheet and bake 15 minutes until cheese is melted. Top with sour cream.