Preheat the oven to 350°F. Grease a 9x9-inch baking pan or line it with parchment paper.
In a mixing bowl, combine the flour, granulated sugar, softened butter, vanilla extract, and salt. Mix until crumbly. Press the mixture evenly into the bottom of the prepared baking pan to form the crust.
In another bowl, beat the softened cream cheese and powdered sugar together until smooth. Add the egg and mix until well combined.
In a separate bowl, toss the chopped rhubarb with lemon juice and cinnamon. Spread the rhubarb evenly over the crust in the baking pan.
Pour the cream cheese mixture over the rhubarb, spreading it evenly.
Bake for 30-35 minutes, or until the edges are lightly golden and the center is set. Allow to cool completely in the pan before cutting into squares.
Serve chilled or at room temperature.