Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking dish with butter or non-stick spray.

Chop the rhubarb into bite-sized pieces and spread it evenly across the bottom of the prepared baking dish.

Sprinkle the strawberry gelatin powder over the rhubarb, followed by an even layer of sugar.

Evenly distribute the yellow cake mix over the rhubarb and gelatin without stirring.

In a small bowl, mix the melted butter, cold water, vanilla extract, and salt, then pour over the cake mix in a zigzag pattern.

Bake for 45–60 minutes or until the top is golden brown and the center jiggles slightly.

Allow the cake to cool at room temperature for 15–20 minutes before serving with ice cream or whipped cream.