Situation : I want to search for the word, 'confedit' in all makefiles in my system using grep.

I have tried :
I know of grep -r
I tried doing grep -r 'confedit' ./*Makefile 2>/dev/null
but it doesn't return anything.

The makefiles could be named as Makefile or makefile.
So please give me a file pattern which checks both.

Please advise,