Melt butter in a pot over medium heat until it turns light amber and smells nutty.
Add apple cider, bring to a boil, and let it reduce into a thick caramel, about 18-20 minutes.
Grease a 9×13-inch baking pan and combine sugar and cinnamon in a small bowl.
Add one bag of marshmallows and salt to the caramel, stir until melted and caramelized.
Remove from heat, add the remaining marshmallows, then mix in rice cereal.
Quickly transfer the mixture to the prepared pan, press it evenly, and sprinkle with cinnamon sugar.
Let it set for at least 1 hour before cutting into delightful squares. Enjoy the taste of fall!