What went wrong with my brownies?
I'm gonna go out on a limb here and say...underbaked.

Either you didn't leave it in long enough or your oven wasn 't hot enough.  Realize many, many ovens can be significantly off their 'set' temperature.  An oven thermometer is a great investment.

(I don't believe applesauce had anything to do with this unless you put like 10x the amount of applesauce in.)