Ingredients:

4 cups rhubarb, chopped
1 1/2 cups sugar
1/2 cup water
1/2 teaspoon ground cinnamon (optional)
1/4 teaspoon ground ginger (optional)

Directions:

Cook the rhubarb: In a medium saucepan, combine the chopped rhubarb, sugar, and water. Bring to a boil over medium-high heat. Reduce heat and simmer for about 20 minutes, stirring occasionally, until the rhubarb is tender and has broken down.
Blend the mixture: Use an immersion blender to puree the rhubarb mixture until smooth, or transfer it to a blender and blend in batches.
Cook the puree: Return the puree to the saucepan and simmer over low heat for about 30-40 minutes, stirring frequently until it thickens to a spreadable consistency.
Add spices (optional): Stir in the ground cinnamon and ginger if desired, and cook for an additional 5 minutes.
Cool and store: Allow the rhubarb butter to cool before transferring to jars. Store in the refrigerator for up to 2 weeks, or process in a water bath for longer shelf life.

Tips & Variations:

You can adjust the sweetness by adding more or less sugar depending on your preference.
Experiment with different spices like nutmeg or allspice for a unique twist.