The Onion ring thingy only appear sometimes for newer Aspherical designs, cast elements? so far I have only seen it seldom with the New Noct-Nikkor 58mm 1.4 and it can differ from image to image almost without any change in framing...
I have never ever seen onion rings in the out of focus highlights in images from the Noct-Nikkor... Nikon claimed it was a hand grinded Aspherical element...
The Leica M 50mm Summilux 1.4 Asph and pre Asph + Leica M 50mm Summicron 2.0 Apo and Pre-Apo are candidates for smooth Bokeh as well!
Although IMHO it is not only the choice of lens but also an exercise in PP not to tweak too much with the 'sliders' in PP when 'developing' the images...
Often now a days online I see contrast, detail and sharpening turned up so much that the Bokeh suffers. So watch out