Rinse the rhubarb thoroughly and trim the ends. Slice it into 1-inch pieces. Place the rhubarb pieces into a heavy-bottomed pot along with the sugar. Add a squeeze of fresh lemon juice and 2 tablespoons of water. Give it a good stir to combine all the ingredients.

Heat the mixture over medium heat, stirring constantly. Let it cook until the rhubarb starts to release its juices and the mixture comes to a gentle boil. This should take around 15-20 minutes. Keep an eye on it to prevent burning.

Once the rhubarb is soft and mostly broken down, transfer the mixture to a blender or food processor. Be cautious when blending hot foods to avoid any accidents. Blend until you achieve a smooth consistency.

Return the puree to the pot and bring it back to a boil. Reduce the heat and let it simmer gently for about 20 minutes, stirring frequently. Watch closely to prevent scorching. As the rhubarb butter cooks, it will darken slightly and become glossier.

To check if it's done, drag a spoon across the bottom of the pan. If the jam doesn't fill in the space, it's ready. The butter will thicken further upon cooling.

Transfer the finished rhubarb butter into a glass jar. Allow it to cool completely before sealing and refrigerating. It will continue to thicken as it cools. This recipe yields about 1.5 cups of delicious rhubarb butter.