Discard 1/2 of the juice from the peaches and pour the rest into a saucepan. Sprinkle the top with cinnamon and sugar. Empty the cake mix on top of the peaches in an even layer. Place the margarine on top of the cake mix in the center.
Cover sauce pan with a lid and bring to a simmer over medium-high heat. Once you see steam escaping the saucepan, reduce heat to medium-low, and continue cooking for 10 minutes. Do not lift the lid during this time! Remove from heat and allow to stand with the lid on for 15 minutes before serving. The cake mix should look like dumplings.
