Wash the rhubarb stalks thoroughly. Trim off the very ends and any leaves (rhubarb leaves are poisonous and should not be consumed). Chop the rhubarb into 1-inch pieces.

In a medium saucepan, combine the chopped rhubarb, granulated sugar, and water. Add a pinch of salt if desired.

Place the saucepan over medium heat. Bring the mixture to a gentle simmer, stirring occasionally.

Reduce the heat to low, cover the saucepan, and let it simmer for 10-15 minutes, or until the rhubarb is very tender and has broken down, forming a sauce-like consistency. Stir occasionally to prevent sticking.

Remove the saucepan from the heat. Stir in the vanilla extract, if using. For a smoother sauce, you can mash any remaining large pieces with a fork or potato masher. For a chunkier sauce, leave as is.

Let the rhubarb sauce cool completely before serving. It will thicken further as it cools. Serve warm or chilled.