Preheat the oven to 400 degrees F (200 degrees C). Prick potatoes several times with a fork and place onto a baking sheet.
Bake in the preheated oven until potatoes are easily pierced with a fork, about 1 hour.
Remove from the oven and lower temperature to 350 degrees F (175 degrees C). Cut potatoes in half lengthwise. Scoop out the pulp and reserve the shells.
Mix the pulp with sour cream, Cheddar cheese, butter, onion dip mix, salt, and pepper. Spoon mixture back into the shells and sprinkle the tops with paprika.
Bake in the oven until heated through and cheese is melted, about 25 minutes.