there is corn flour, that hispanic folks
use for making corn tortillias and tamales,
and is called masa. that is not used for
making cornbread. most masas have been
treated with lime during processing.
corn meal is simply untreated plain
coarsely ground dried corn. maybe if you
used masa the lime is the bitterness?
also, if you use buttermilk in your cornbread,
you're supposed to use baking soda. if
you use sweetmilk, you use baking powder.
the different leavenings react differently
with the different types of milk.
maybe that is the bitterness?
better luck next time, or just buy jiffy mix.