1.Where is it that you told me to bring home?
2.Where is it, which you told me to bring home?
("It" is not a place but an object such as bag or apple)
I think both are natural and grammatically correct because as for 1, I need to use "that" so as to specify what is "it" I'm referring to if "you" seem to be not sure what I'm indicating, but as for 2, I don't need to use "that" to specify "it" if "you" have already known well what is "it", so just to add information, "which" seems to be a better choice in this case than "that". But if they are not natural as well as grammatically wrong, though my assumption is possible, could you answer this question with your natural-sounding examples?