Let the butter come to room temperature, it should be very soft but not melted.
In a stand mixer with the whisk attachment or with a hand mixer, beat the butter on medium-high speed until light and fluffy, about 3–4 minutes.
Drizzle in the sorghum syrup, vanilla, and sea salt (plus cinnamon if using). Beat again until fully combined and airy.
Spoon into a jar or small crock. Serve at room temperature or chill for later, it will firm up beautifully.