Optical microcavities provide a powerful and versatile framework for manipulating the dynamics of photonic emission from optically active materials through light recirculation. Spatially indirect interlayer excitons (IXs) exhibit broad tunability of their emission energy via the quantum-confined Stark effect. However, the electrical tunability of IXs has not been exploited in cavity-coupled systems until now. Here we modulate the detuning between the cavity resonance and the IX emission in a monolithic Fabry–Perot cavity using an applied vertical electric field. We reveal a simultaneous enhancement of both the emission intensity and lifetime of weakly coupled IXs when in resonance with the optical cavity owing to strong Purcell inhibition and cavity transparency effects. We further investigate the tunable momentum dispersion of coupled IXs through back-focal-plane imaging and explain our results by the cavity coupling of IX transition dipoles as supported by theoretical modelling. Our work demonstrates an integration effort enabling the versatile tuning of highly interacting IXs within monolithic cavities, revealing the attractiveness of electrically tunable IX cavity coupling for both fundamental studies towards exciton condensate manipulation and future integration of excitonic devices.