A torx 27 or 30 may be the ticket. Maybe. There are also some small "spline" drive bits. Or triple square drive bits.
If you do not have them lying around... I do but bought sets for a few projects over time.. I would do as previously suggested and drill two 3/32" or so holes near the perimeter, reference another cap to stay inside the threaded section, then a pin wrench or something to use as a drift, part of the trick is to have the bike restrained.
Penetrant is useful and a initial step.
Been here a number of times, the chrome is hard, the material below is not, be sure to use a punched locator point to prevent drill wander.

This is the reason that I do not like crank bolt dust caps.