Beat the butter with an electric whisk or in a small blender until pale and fluffy. Finely grind the long pepper using a pestle and mortar. Stir the pepper into the whipped butter with the orange zest and a pinch of salt, if you like, then whip in the orange juice until it is combined. Spoon into a dish or shape using a waxed wrap or parchment and chill until needed. Will keep for one week. Serve with bread or dot over steamed spinach or greens.