In a large pot or large saucepan, brown the rabbit in the butter for about 15 minutes. Season with salt and pepper. Add the onion and sauté for about 5 minutes. Deglaze the pan with the rum. Add about 125 ml (1/2 cup) of carrot juice. Cover and simmer gently for about 25 minutes, adding 30 to 45 ml (2 to 3 tablespoons) of carrot juice every 3 to 4 minutes.