In a medium bowl, combine sugar, flour, egg yolks, milk, and salt.
Using a mixer, beat on high speed for about 1 minute or until pale and fluffy.
Pour over rhubarb.
Bake at 400 F (200 C) for 20 minutes. Reduce oven heat to 350 F (175 C) and bake for 20 to 30 minutes longer or until a thermometer inserted in the center reads about 90 C.