Preheat the oven to 400 degrees F (200 degrees C).
Lay out 4 squares of aluminum foil on the counter. Cut each potato in half lengthwise, and place onto a square of aluminum foil. Place 1/2 tablespoon of butter onto the cut side of each half, then season with garlic powder and salt. Close the potato halves together, and wrap tightly in the aluminum foil.
Bake potatoes directly on the oven rack for 40 minutes, or until tender.