Prep a standard loaf pan by lining with parchment paper. I like to spray the pan so the parchment paper sticks. This makes it easier to line the pan.
In a medium bowl, combine the flour and powdered sugar. Using a pastry blender or your fingers mix the butter into the flour and sugar until the mixture resembles coarse crumbs.
Gently pat the crumbs into the base of your prepped loaf pan. Bake the crust for 10-12 min or until lightly browned.
While the crust is in the oven, mix together eggs, sugar, flour, vanilla extract and salt. Gently stir in the diced rhubarb.
Pour the rhubarb mixture over the hot crust. Carefully return bars to the hot oven. Reduce oven temperature to 325℉ and bake for 30-35 minutes, or until the filling is set and no longer jiggles.
Cool for 30 mins on the counter. Refrigerate until chilled before cutting into bars. Refrigerator any leftovers.