In a heavy bottomed pot, heat the olive oil over medium-high heat. Add the onion, chard stems (not leaves!) and squash. Saute until the squash is tender.
Add the cranberries and cinnamon stick. As the berries heat, they will often pop...this is normal, so don't be scared! Allow the cranberries to soften until edible.
Add the zest, vinegar and spices. Stir until fragrant (about 1 minute), then turn off the heat and immediately add the chard leaves. Stir and season with salt and pepper until wilted to your level of desired doneness.