It is not correct to say on tomorrow, on yesterday, or on today. These words are adverbs and do not require the preposition "on". Prepositions require an object. Since days of the week are nouns, they are objects for prepositions. It is incorrect to assume it is OK to use 'on' with all expressions of time. The redundancy is not that the word 'to' is in tomorrow. The redundancy is that tomorrow, is an adverb that already designates a place in time, and does not require a preposition.

Although it has become common usage in some parts of the county to say 'on tomorrow (yesterday, today), it is poor grammar and makes even the most educated person sound stupid.