I have lots of stuff I could bore you to death with!
but you said CNC mill and not on anything else so my vote is a cnc mill with an standard bottom cutting end mill. and hold the piece in a three jaw. If you have a toolchanger then drill it first otherwise circular interpolate and finish at depth! walla! flat bottom hole with automation.
of course lathes were made for these roundish kinda parts. But you said CNC and I am naturally lazy so the mill wins.