Cut off all but 1-inch of the carrot tops, leaving a little green. Put the carrots in a large shallow pan, add the oil, and season with salt and pepper. Turn to coat the carrots. Stick them in the oven and bake for 30 minutes, until the carrots are fork-tender.
In the meantime, melt the butter in a skillet over medium-low heat. Swirl the pan around and cook until the butter begins to become brown and nutty. Squeeze in the juice from the orange halves, add the zest, brown sugar, cumin and cinnamon and continue to cook for 2 minutes or until syrupy.
Remove the carrots from the oven, drizzle the orange brown butter over the carrots and serve.