Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking pan.

In a large bowl, whisk together the flour and powdered sugar. Cut in the cold butter until it resembles coarse crumbs.

Press the mixture firmly into the bottom of the prepared pan and bake for about 15 minutes until lightly golden.

In a medium bowl, combine the chopped rhubarb and granulated sugar, allowing it to sit for about 10 minutes.

In another bowl, beat the eggs, then mix in the flour and vanilla extract. Fold in the rhubarb mixture.

Pour the filling over the baked crust and return to the oven to bake for an additional 30 to 35 minutes.

Remove from oven and cool for at least 15 minutes before refrigerating for 1 hour.

Slice the bars into squares and serve chilled or at room temperature.