Magnonics uses spin waves and their quanta, magnons, to carry and process information and offers new opportunities for computing and signal processing. Its integration with conventional electronics, however, requires scalable electrical interfaces for magnon readout. Here, we demonstrate electrical magnon spectroscopy using a 70-nm magnetic tunnel junction fabricated on a commercial 300-mm semiconductor production line. Dynamic dipolar fields generated by magnons in a magnetic vortex drive the free layer of the tunnel junction and are transduced into electrical signals through tunnelling magnetoresistance. By exploiting three-magnon splitting, we spectrally separate the magnon response from direct microwave excitation and resolve nonlinear magnon modes with linewidths down to 188 kHz at 3.59 GHz. The electrical measurements reveal spectral structure that remains unresolved in parallel Brillouin light scattering measurements. Our results establish foundry-fabricated magnetic tunnel junctions as nanoscale electrical interfaces for magnonic systems and provide a route towards their integration with semiconductor electronics.