Preheat the oven to 425 degrees F (220 degrees C). Grease an 11x7-inch baking dish.

Mix together 1 cup flour, butter, and 1 tablespoon sugar in a large bowl until well combined; press into the bottom of the prepared baking dish.

Bake in the preheated oven until golden brown, about 10 minutes. Remove crust from the oven and set aside. Reduce oven temperature to 350 degrees F (175 degrees C).

Combine 1 cup sugar and remaining 1/4 cup flour in the same large bowl; stir in rhubarb and toss to coat. Spread rhubarb mixture over crust.

Mash together cream cheese, 1/2 cup sugar, and egg in the same large bowl until creamy and well combined; spread over rhubarb.

Bake in the oven until rhubarb is bubbling and topping is set, about 35 minutes.

Meanwhile, mix together sour cream and 1 tablespoon sugar in the same large bowl until well combined.

Spread sour cream mixture over hot dessert. Allow to cool completely before cutting into bars. Refrigerate leftovers.