On a cutting board, place each apple flat side down. Using a paring knife, create thin slices all the way across; try to stop slicing right before the bottom so it stays together as one piece.
Transfer apple halves to baking sheet. Lightly brush apples with 2 Tablespoons butter and sprinkle with sugar.
Bake approximately 25 minutes or until apples are soft.
Remove apples from oven. In a small bowl, combine remaining butter, sugar, cinnamon and oats. Spoon mixture inside apple slits.
Return to oven and bake 10 minutes more.
Top each serving with a scoop of ice cream, if desired.
Notes
NOTE: carbohydrates listed are NET carbs and nutritional information does NOT include ice cream.