Translation:Here you go; I made you some vanilla cookies.
"You Go" is completely superfluous, and impossible to deduce from "tenir". "Here. I made you some cookies is the best fit IMHO, and to my thinking, even though Jojo553168 disagrees, with all due respect to Jojo, I am addressing the common sense of the translation of "tenir" to "Here you go", which just doesn't wash at all. "Hold it. I made you some cookies" makes more sense, although it may not be what the native speaker intends.