Wash and cut the acorn squash in half. Scoop out all the seeds with a spoon.
Score the inside of the squash with a knife. You will want to score it horizontally and vertically so that you end up with squares on the inside fleshy part of the squash.
Mix together the brown sugar, cinnamon, and salt together in a small bowl or ramekin.
Place 1 tbsp of butter in each of the halves of the acorn squash. Slightly spread the butter around the squash.
Add half of the mixture to one of the squash. Add the other half to the other squash.
Then spread and mush the butter and mixture into the inside of the squash.
Place each of the squash halves in the air fryer basket. Cook 370 °F for 25 minutes.
Test with a fork to make sure the squash is tender and cooked through.