In a medium saucepan, combine 2 cups of chopped fresh rhubarb, 1 cup granulated sugar, and 1/2 cup of water along with 2 tablespoons of cornstarch. Cook over medium heat, stirring gently until the rhubarb becomes tender and the mixture thickens, about 10–12 minutes. Once thickened, remove from heat and allow it to cool.

Preheat your oven to 350°F (175°C). In a bowl, mix 1 1/2 cups of graham cracker crumbs with 1/2 cup melted butter until well combined. Press the mixture firmly into the bottom of a 9-inch baking dish. Bake for 8–10 minutes until golden and fragrant, then remove from the oven and let it cool completely.

In a large mixing bowl, beat together 8 ounces of softened cream cheese and 1 cup of powdered sugar until smooth and creamy, about 3–5 minutes. Gently fold in 1 cup of whipped topping until fully incorporated. Spread this mixture over the cooled graham cracker crust.

Spread the cooled rhubarb mixture evenly over the cream cheese layer. Let it chill at room temperature for about 15 minutes.

Spread the remaining 1 cup of whipped topping over the cooled rhubarb layer, smoothing the surface with a spatula.

Cover and refrigerate for at least 2 hours to allow the layers to set before slicing.