I just tried a new recipe, which called for3 sticks of unsalted butter. By accident, one of the sticks, I put in was salted. The cake is now in the oven ( yellow cake), and it is getting VERY brown. It also spilled over the sides and made a mess in my oven. Was this because I used the wrong butter?

I highly doubt the butter is the cause of the browning or spilling over. I use salted and unsalted in my baking with no problem. Maybe it spilled over because the pan wasn't deep enough or large enough. I had that happen once, the spilling over, and it was because my oven wasn't heating evenly. Haven't had that happen again since purchasing a new oven.

Check your oven by purchasing an oven thermometer, they are cheap, also use a deeper or larger pan next time. Maybe the one you used didn't give it enough room to rise properly.

Hope that helped a bit. Good Luck & Happy Baking

Did you over fill the pan? It's definitely not the butter.

Aside from the problems the OP had, do all of you use salted or unsalted butter in your cakes & icings?

TIA!
Kimm

I use unsalted always.

I always use salted!

For cakes I use whatever I have on hand, but for buttercream icings I use what the recipe recommends.