Spread the soft butter all over the dough, leaving 1 inch along the longest rectangular edges. This will allow you to close the roll once it's ready and ensure it doesn't open up while baking.
In a separate bowl, combine the brown sweetener with cinnamon, then spread the "cinnamon sugar" on top of the dough greased with butter. Leave the same 1 inch along the edges untouched.
Distribute finely chopped apples on top of the cinnamon filling.
Roll dough starting from one of the longer edges. Keep it tight, but don't press it. Once you've reached the other long edge, pinch it to close.
Cut the long roll into even pieces, approximately 1-inch thick. You'll end up with approx. 18-20 pieces.
Transfer the roll pieces to a greased baking dish (alternatively, transfer to a baking tray, lined with parchment paper), cover with a towel, and leave it for a second rise (about an hour). Remember to leave some space between the rolls to allow for rising (I leave about an inch or so).