Spread the rolled oats flat in a large pan.
Bake in a preheated 325°F (160°C) oven for 10 minutes.
Remove from the oven and set aside.
Meanwhile, in a saucepan stir together the apple juice concentrate and cornstarch and cook over medium heat until thickened, stirring constantly.
Spread the nectarine slices evenly over the bottom of a small ovenproof dish that has been coated with non-stick cooking spray.
Pour the apple juice-cornstarch mixture over the slices.
Then combine the flour, cinnamon, nutmeg, and acesulfame-K with the oatmeal.
Add the pancake syrup and sour cream to the flour-oatmeal and stir to combine.
Crumble this mixture over the nectarines.
Bake in a preheated 325°F (160°C) oven for 45 minutes.