The noun from the verb to pronounce is pronunciation, meaning 'the way a speaker produces the sounds of a word or of a language'. It has lost an -o- on the way.
There is also a noun pronouncement, but it has a rather different meaning. It means a rather formal statement of facts or opinions that may have been in doubt. A professor may pronounce upon a dispute between two of her students - that is, give a scholarly decision about which of them is right; or a doctor may pronounce upon a health problem - that is, say what is wrong; or a judge may pronounce upon a case - that is, give a decision as to who 'wins'. The noun pronouncement is the correct way to name an example of each of these uses of pronounce.