I just made a WASC which I have made numerous times and never had a problem.
(2) 8" cakes
(1) 6" cake
used bake even strips
put parchment on bottom
baked at 325
The only thing I did differently was I used a DH mix instead of BC. Do you think the different mix is why it split?
I use DH all the time and never have a problem, so I doubt that is the issue. Did you possibly overbake?
me too always have a dome and split top cake, never get the flat smooth cake. I try to shorten the baking time and lower the temperature and it come out better but still have a minor split and dome. But when I use a wet towel to wrap around the pan and it come out just nice and smooth. Why not you try this method and also rap the pan a few time before you bake, this may help.
Split as in it had a crack in the top when it came out of the oven? I always use BC with the extender recipe and once in a great while may have a crack, but wouldn't call it a split. Is it split so badly you cannot use it? Did it rise as it always did and not appear to have that volcano rise in the middle after the outsides have baked?
Are you positive your oven was at 325? I ask because before I bought a new oven that resets itself automatically to 350, I had assumed my oven was on 325 and didn't realize the DS had put a frozen pizza in the night before. (Lonnngg time ago...) and had all kinds of problems with that cake including a fat split from baking too quickly.
I usually only get cracks when I walk away and overbeat the batter. Trying beating for less time and see if that helps.