Prep the rhubarb: Rinse the stalks, trim the ends, and chop into small pieces.
If using frozen, no need to thaw.
Combine in a pot: Add rhubarb, sugar (or honey), vanilla, lemon juice, water, and a pinch of salt to a medium saucepan.
Bring to a gentle simmer: Set over medium heat. Stir as the rhubarb releases juices. When it starts to bubble, reduce to low.
Cook until soft: Simmer 8–12 minutes, stirring occasionally, until the rhubarb breaks down and looks saucy.
A few tender chunks are fine.
Adjust sweetness: Taste carefully. Add a little more sugar or honey if your rhubarb is very tart. Stir to dissolve.
Thicken if needed: If you like it thicker, cook 2–3 more minutes.
For a smoother texture, mash gently with a spoon.
Finish and cool: Remove from heat. Stir in any optional spices or zest. Let cool for 10–15 minutes before serving warm, or chill.