I have seen the spelling amature on websites enough times to notice, but have never commented about it, either on those websites or here. I have just seen the spelling amuture.
The correct spelling is amateur. Different dictionaries give its etymology as ama + teur and others as amat + eur, but the difference doesn’t matter. An amateur is a lover of what they do. Some amateurs are very, very good at what they do, but Dictionary.com’s third definition is “an inexperienced or unskilled person”. It has just occurred to me that amature might be a (not) + mature, but that would be adding a Greek pronoun to a Latin root (which does happen). (By the way, the original Latin spelling amator seems not to be used.)
Google has an ambivalent attitude towards amature. A simple search returns “Your search – amature – did not match any documents”. But clicking on ‘images’ shows many, many titled as ‘amature image’, ’amature model’ etc. Clicking on ‘videos’ returns “Your search – amature – did not match any video results”. Clicking on ‘news’ gives many stories from media sources with headlines such as ‘Lucy Li and one other withdraw from the Augusta National Women’s Amature’ and articles such as ‘He was also an avid singer acting as an amature actor in many plays in the area, he especially loved singing broadway tunes’ (which also has a problem with commas).
At no point does it suggest either amateur or mature. A search for amuture immediately asks “Did you mean: mature” (but not amateur).
Google Ngrams shows no results at all for amuture. Amature shows a slight rise since 2000, but shows as close enough to a flat line against amateur. Pages for Mac autocorrects amature to amateur, but leaves amuture alone (but red-underlines it). I can only assume that occurrences of amature are created on programs without an autocorrect or spellchecker, or that the users haven’t turned it on, or that they ignore it, or that they simply don’t care.
‘Amature’ looks so … amateur (in the “unskilled” sense). However, worse spelling mistakes have taken root in history, and are taking root now, despite autocorrect and spellcheckers. I doubt that amature will ever become an accepted spelling, let alone the accepted spelling.
Also, Dictionary.com gives the pronunciations of –choor and –cher first, followed by –ter and –tur. I think that in casual speech, I would say -tə, and in careful speech -tɜː.