B767 Captain reported an abrupt onset of turbulence resulting in the aircraft roll to 35 degrees. Flight crew executed the UPRT procedures; descended to a smoother altitude and continued to flight with no further issues.

Narrative

TurbulenceApproximately 100 NM W-NW of the waypoint ZZZZZ Aircraft X encountered clear air turbulence; most likely caused by jet stream influences. The Captain (PM (Pilot Monitoring)) and the OE Captain (PF) (Pilot Flying) had just returned to their respective seats and were completing their turnover briefs with the IROs at the time of the event's occurrence. Shortly after the PF fastened his seatbelt; we encountered an abrupt onset of turbulence resulting in the aircraft rolling up to 35 degrees. The PF immediately disconnected the autopilot and began gingerly executing UPRT procedures with consideration of the aircraft's operating envelope.Simultaneously; the PM; requested and received clearance to descend to FL320. The aircraft was stabilized and we were able to level off at FL340 in smooth air. There were no injuries to passengers or crew and no aircraft limits or normal flight parameters were exceeded.(i.e. No UAS occurred). ATC was further notified as to the location and altitude of the event so as to make other aircraft aware and when time permitted the PM notified Dispatch as well. Dispatch acknowledged severe turbulence report and said they would notify Maintenance Control.