Preheat the oven to 350°F (175°C). In a mixing bowl, combine flour, sugar, melted butter, and salt. Mix until crumbly.

Press the mixture into the bottom of a greased 9x13 inch baking pan. Bake for 10-12 minutes until lightly golden.

In a mixing bowl, beat the softened cream cheese until smooth. Add sugar and vanilla, mixing well.

Add the eggs one at a time, mixing well after each addition. Stir in sour cream until combined.

Pour the cheesecake filling over the baked crust and spread evenly.

In a saucepan, combine chopped rhubarb, sugar, cornstarch, and water. Cook over medium heat until rhubarb is tender and mixture thickens.

Spread the rhubarb topping over the cheesecake filling.

Bake the assembled cheesecake squares for 45-50 minutes until set. Let cool completely in the pan.

Refrigerate for at least 4 hours before cutting into squares and serving.