Definitions of the ampere and coulomb.Watch
Obviously the definition of an ampere is slightly more complex in reality, but the above is just using definitions and SI units.
the coulomb is a derived unit from the SI base units for current and time (Amp and second)
it wouldn't be a very sensible thing if the SI units really had circular definitions for obvious reasons
The coulomb (not a base SI unit) is then defined in terms of this current and the time of 1 second. The second is also a base SI unit.
There is no cross reference in terms of the basic SI definition of the two.
They are related via time in
current = charge / time.
Is this what you mean?