Preheat oven to 400*.
Butter bottom and sides of large oven proof bowl (such as Pyrex) with butter.
Meanwhile, mix together sugar, flour, nutmeg and salt, add to the beaten eggs; beat till smooth.
Stir in rhubarb slices.
Fill oven proof bowl. Dot the top with slices of butter. Cover with tinfoil and bake 50 minutes. Remove tinfoil and bake an extra 10 minutes or till rhubarb is tender.