2Process flour, butter, and 1/4 cup sugar together in a food processor until crumbly; press mixture into bottom of 9x9-inch baking pan.
3Bake in preheated oven until golden brown, about 15 minutes.
4Stir rhubarb, egg, 1/4 cup sugar, and almond meal together in a bowl until combined; spread mixture over crust.
5Bake in preheated oven until bubbling, about 30 minutes.
6Cool to room temperature on a wire rack before cutting into bars.
Footnotes
Cook's Note:
For the crust, if you don't have a food processor you can easily cut the cold butter into the flour and sugar with a knife or pastry blender until the mixture resembles coarse crumbs.