Doom wins. All he needs to do in those 30 seconds is charge his shield with offensive magic. Battle starts - Superman runs into Doom's shield - Superman dies.
But if he doesn't know about his magic weakness he won't summon a super duper magic shit from the start, and superman weakness isn't very consistent on its extent.
The same way nearly ever supervillain that's used magic against Superman knows. They heard about it and/or they discover it immediately during a fight.
If Doom is not told who he is up against with prep he will prepare for worst case scenario. That being said his magic could possibly give him a lucky win or two but superman takes the solid majority. Doom is a really exquisite character-I just purchased the new sideshow exclusive with the embroidered armor that's 35 pounds lol
Doom's shields can tank Johnnie's supernova, which is more or less about the same heat as Superman's heat vision. The heat vision bounces off Victor's shield while he proceeds to charge some spell that one shots supes.
Or he just goes xX_H4X_Xx and uses ovid mind switch, leaving him a nice new Kryptonian body to play around in.
30 seconds prep jesus quanchi.smarter? not really superman is as smart as they come he just isn't acostumed to planning things out he leaves that to batman. Doom could win with A lot of prep but not 30 seconds. But then again you know that you just hate D.C. P
As far as supes weakness to magic its overrated. This isn't PC supes were talking about here.