Looks to be a chapel or church.....per the property outlines as seen on the Chelan County Asseors page https://maps.co.chelan.wa.us/GIS/ Property ID#30028.
Photo taken from a hike this week, standing above the barn.
It appears to be on the same owners land, but isn't included in the improvements/structures breakdown along with the large barn/hangar. Nor is the other structure above the chapel along the ridge line accounted for by the county.
Both are visible on google maps. 47.52672496244515, -120.6786419076031, and 47.524546797153796, -120.68070380839872
The owners certainly have some resources!