In a large, heavy-bottomed saucepan, combine the blueberries, granulated sugar, lemon juice, and lemon zest. Stir over medium heat until the sugar dissolves and the blueberries begin to release their juices, about 5-7 minutes.
Bring the mixture to a gentle boil, then reduce the heat to low. Simmer for 20-25 minutes, stirring occasionally, until the blueberries have softened and the mixture thickens slightly.
Using an immersion blender (or transferring in batches to a standard blender), puree the mixture until smooth. Be cautious with the hot liquid.
Stir in the cinnamon, nutmeg, and vanilla extract. Continue to simmer on low heat for an additional 30-40 minutes, stirring frequently, until the mixture reduces to a thick, spreadable consistency similar to jam. It should coat the back of a spoon.
Remove from heat and stir in 1 tablespoon honey for a glossy, sweet depth. Let cool slightly.
Transfer the blueberry butter to sterilized glass jars or an airtight container. Let cool completely before sealing.
Spoon the blueberry butter into a small serving dish or directly onto toast, scones, or pancakes. Drizzle a little extra honey over the top for a glossy, sweet accent that enhances the blueberry flavor.
Garnish with a few fresh blueberries and a sprig of fresh thyme or scatter edible flowers for a vibrant, elegant touch.
