Preheat oven at 350 degrees F.
Cut the plums in half, and remove the pits. Place the plums in a baking dish, skin-side down, and sprinkle with sugar, and cinnamon, and grate a little lemon zest over the top.
Place the baking dish in the oven and roast for about 30 minutes, or until soft.
Serve over warm bread that has been buttered or 'buttered and honeyed.'