Preheat the oven to 350°F (175°C) and line a 9x13-inch baking pan with parchment paper.

In a mixing bowl, combine 2 cups of all-purpose flour with 1/2 cup of granulated sugar. Cut in 1 cup of softened butter until resembling coarse crumbs. Press into prepared pan.

Bake the crust for 15-20 minutes or until light golden brown. Let cool slightly.

In a separate bowl, whisk together 3 eggs until frothy. Gradually mix in 1 1/2 cups of sugar, 1/2 cup of flour, and 1/2 teaspoon of baking powder. Fold in 3 cups of chopped rhubarb.

Pour the filling over the cooled crust and bake for an additional 40-45 minutes until set and lightly golden.

Cool completely in the pan, then lift the parchment to remove the bars and slice for serving.