Preheat your oven to 350°F (175°C) and prepare a 9×13-inch baking pan by lining it with parchment paper or lightly greasing it.

In a mixing bowl, combine 2 cups of all-purpose flour, ½ cup of powdered sugar, and a pinch of salt. Cut in 1 cup of cold butter until the mixture resembles coarse crumbs, then press into the bottom of the prepared pan.

Bake the crust for 15–20 minutes, or until it is lightly golden around the edges. Let cool slightly.

In a separate bowl, whisk together 3 eggs until frothy, then mix in 2 cups of granulated sugar, ½ cup of all-purpose flour, and ½ teaspoon of baking powder until smooth. Gently fold in 3 cups of chopped rhubarb.

Pour the rhubarb filling over the pre-baked crust, spreading it evenly. Return to the oven and bake for 40–45 minutes.

Let the bars cool completely in the pan before slicing into squares or rectangles.