  We report the observation of an unusual cold, tenuous solar flare, which
reveals itself via numerous and prominent non-thermal manifestations, while
lacking any noticeable thermal emission signature. RHESSI hard X-rays and
0.1-18 GHz radio data from OVSA and Phoenix-2 show copious electron
acceleration (10^35 electrons per second above 10 keV) typical for GOES M-class
flares with electrons energies up to 100 keV, but GOES temperatures not
exceeding 6.1 MK. The imaging, temporal, and spectral characteristics of the
flare have led us to a firm conclusion that the bulk of the microwave continuum
emission from this flare was produced directly in the acceleration region. The
implications of this finding for the flaring energy release and particle
acceleration are discussed.
