Wash and chop the rhubarb into small, even pieces (about 1/2 inch thick).
Zest the orange using a microplane or zester. Then juice the orange using a citrus juicer.
in a medium to large saucepan, combine the chopped rhubarb, honey, orange juice, orange zest, vanilla extract, and ground cinnamon. Add the cinnamon sticks, star anise adn allspice.
Place the saucepan over medium-low heat. Stir the mixture well to combine all ingredients.
Bring the mixture to a gentle simmer. Cook for about 20-30 minutes, stirring frequently. The rhubarb should soften and break down completely.
Once the rhubarb is completely softened, remove the saucepan from heat. Remove cinnamon sticks, star anise and allspice.
Use an immersion blender to puree the mixture until smooth directly in the saucepan. If using a regular blender, allow the mixture to cool slightly, then blend in batches until smooth. Be cautious with hot liquids.
Taste the rhubarb butter and adjust sweetness or spices as needed. You can add a bit more honey or sugar if it’s too tart, or more spices if desired.
If the rhubarb butter is too runny, return it to the heat and simmer gently until it reaches your desired thickness. Stir frequently to prevent burning.
Notes
Choose Fresh Rhubarb - select firm, brightly colored stalks for the best flavor. Avoid any stalks that are limp or have blemishes.Control sweetness - rhubarb is naturally very tart, so adjusting the sweetness to your taste is important. Start with the recipe's suggested amount of sweeteners, then adjust as needed.Simmer - the rhubarb mixture over medium-low heat. Cooking it slowly helps to bring out the flavors and prevents burning.Blend thoroughly - use a blender or immersion blender to puree the mixture until smooth. This ensures a consistent texture for the butter.