Make the cinnamon sugar filling by adding the softened butter, sugar, and cinnamon to a large bowl and mixing until smooth with a whisk or hand mixer.
When your dough has doubled in size, remove it from the bowl onto a lightly floured surface.
Roll out the dough with a rolling pin into a large rectangle, ½ inch thick, about 12" wide, and 15" long.
Smear the cinnamon-sugar mixture on top of the rolled-out dough, leaving about ½ inch of space along the outside edges of the dough.
Sprinkle pecans on top of the dough, making sure to evenly space them out.
Tightly roll from the long side of the dough into a log shape.
Score 8 evenly-spaced sections in the top of the dough with a sharp knife, then carefully cut them into buns. The dental floss trick unfortunately won't work because it can't cut through the pecans, so a serrated knife works best.
Assemble the cinnamon buns in your prepared pan on top of the glaze mixture. It's okay if they are almost touching, just make sure that your pan is big enough to easily fit all of the buns. They will proof again before baking.
Cover the pan with a clean kitchen towel and place them in a warm area for 30 to 60 minutes until the buns are crowded in the pan and poofy. They don't have to be fully doubled in size, but your rise time will also be determined by the size of your pan.