Context : Large cavities in disks are important testing grounds for the mechanisms proposed to drive disk evolution and dispersion , such as dynamical clearing by planets and photo-evaporation .

Aims : We aim to resolve the large cavity in the disk around HD 34282 , such as has been predicted by previous studies modeling the spectral energy distribution

Methods : Using ALMA band 7 observations we study HD 34282 with a spatial resolution of 0.10 \times 0.17″at 345 GHz .

Results : We resolve the disk around HD 34282 into a ring between 0.24 and 1.15″ ( 78 ^ { +7 } _ { -11 } and 374 ^ { +33 } _ { -54 } au adopting a distance of 325 ^ { +29 } _ { -47 } pc ) .
The emission in this ring shows azimuthal asymmetry centered at a radial distance of 0.46″and a position angle of 135 °and an azimuthal FWHM of 51° .
We detect CO emission both inside the disk cavity and as far out as 2.7 times the radial extent of the dust emission .

Conclusions : Both the large disk cavity and the azimuthal structure in the disk around HD 34282 can be explained by the presence of a 50 M _ { \mathrm { jup } } brown dwarf companion at a separation of \approx 0.1″ .