42 kHz is obviously not center frequency if frequency range is 100 kHz wide, Actual frequency range is unknown and maybe is load impedance something that dynamically is changed within this frequency range, as a part of setting frequency of interest. Maybe is bandwidth of interest just the resonant frequency in a certain tunable range.
I'll try to answer according to this.
If you still want to design a matching circuit and you are tuning load with a variable C, then must also matching circuit be tuned correspondingly to the new impedance situation.
A matching circuit can not be designed for more then one fixed situation if designed with fixed components.
The matching circuit internal structure is not relevant as long as it fulfills to be the complex impedance conjugate.
In much does, how I understand your problem, reminds me of how an old superheterodyne radio is designed with a local oscillator and several tuned filters, all controlled by a multi section tunable capacitor.
Looking at a such circuit can maybe give some ideas related to your circuit.
An new alternative seems to be implementing an op-amp without intention to improve impedance matching. Guess you says that wide band impedance matching not really is of interest.
You want a circuit that can feed internal losses in a resonant circuit, without burning the op, at resonance frequency where load is a pure resistive impedance.
Small-signal op-amps have relative high internal serial resistance for the output stage, typical 20-100 Ohm.
If you want to match a such circuit to deliver power in 1 Ohm resistive load more effective can it be done with a regular winded impedance transformer in between. A such transformer can be relative wide band in its behavior.
Adding a PA stage with some low impedance transistors is another possibility.