As I was replacing my transmission, the transmission bolting flange broke off. It's the little bit where the gold plate bolts to. Can this be welded back together? I realize it needs to be very straight for there to be no leaks.. , but, if it wasn't, could I put gasket maker all the way around to seal it up? Bought this car to flip and this happened and now I'm in the hole if this can't be fixed..

 

That's actually the upper oil pan, yes it can be taken off and replaced with a non-broken one.

 

Yes, you can have it welded. A competent welder can fix that with the engine in the car, once it's on a lift - which will require a tow, or a push start, since:

That's where the starter mounts. Having it "slightly off" isn't going to cause "leaks" as there's no fluid on either side of that. But, it needs to be straight to get the starter to engage properly.

If you decide to go that route, and it's probably going to be a LOT cheaper and less trouble than replacing parts, make sure you tell the shop, when you're shopping around, that it's an aluminum block. Welding AL vs steel requires different technique and equipment.

Replacing the upper oil pan, as @cleric670 proposed, is a pretty big PITA and stops just short of having to pull the engine. It's not impossible or particularly difficult - it's just a lot of work. Front cross-member has to come down, etc.