Serve these plums over country-style toast or vanilla ice cream for an easy fall dessert.
Preheat oven to 400 degrees. Arrange plums, cut side down, in a medium ovenproof skillet or baking dish. Sprinkle butter, sugar, orange zest, and pinch of salt over plums. Roast until very tender but still intact, 40 to 45 minutes. Pour orange juice over top; swirl to incorporate. Serve warm.
If your plums are very ripe, the cooking time will be shorter.