Leave the butter out at room temperature at least an hour before beginning - it should yield easily but hold its shape.
Beat the softened butter with a hand mixer, stand mixer, or wooden spoon until it lightens in color and becomes fluffy - about 2 minutes with a mixer.
Drizzle in the honey slowly, beating continuously, until it comes together into a pale, cohesive spread.
Add cinnamon if using and mix well - it should read as background warmth, not dominant flavor.
Transfer to a small crock or jar. Keep at room temperature up to 3 days, or refrigerate up to 4 weeks.