Preheat oven to 375°F (190°C).

In a large mixing bowl, combine halved sand plums, olive oil, honey or maple syrup, and rosemary. Toss well to coat the plums evenly.

Spread the plums on a baking sheet or a cast iron pan in a single layer, cut side up.

Sprinkle with a pinch of salt and freshly ground black pepper.

Roast in the preheated oven for 20-25 minutes, or until the plums are tender and caramelized.

Remove from the oven and let cool slightly before serving.