Preheat your oven to 350°F (175°C). In a mixing bowl, combine 1 cup of flour, ½ cup of sugar, and a pinch of salt. Cut in ½ cup of cold, cubed butter until resembling coarse crumbs. Press the mixture into the bottom of a 9x13 inch baking dish and bake for 20 minutes, until lightly golden.

In a blender, combine 1 cup of freshly squeezed lemon juice, 1 cup of chopped rhubarb, and 2 room temperature eggs. Blend until smooth. In a separate bowl, mix 1 cup of sugar and ¼ cup of flour, then gently fold into the rhubarb mixture along with 1 teaspoon of vanilla extract and the zest of one lemon.

Pour the filling over the hot crust and spread evenly. Bake for an additional 35 minutes, until the center jiggles slightly and the edges are set.

Let the bars cool in the pan for 1 hour on a wire rack. Once cooled, refrigerate for at least 2 hours until fully chilled.

Cut the bars into squares and dust with powdered sugar. Serve with whipped cream or vanilla ice cream for indulgence.