How do you convince a Catholic that the Genesis narrative, not evolution, is true?

I would start with their heart, because it comes down to whom they will believe: the Bible, the Fathers, the tradition, the magisterium, and the history of the Church that taught creation until the intellectuals came along, or figures like Lawrence Krauss and Carl Sagan popping up in videos telling you how old and vast the universe is. If they say they will not trust the Bible because it is an ancient document written by men who erred, and that the Church now teaches only what is necessary for salvation is inspired, then stop the conversation and move on; you will not get to first base without an open heart willing to consider it might be wrong. Your job is not to chase people down but to teach the truth; those whom God is leading will come back and ask for more. To probe where someone is, you can drop a hook, such as, did you know the geologic column said to have formed over millions of years can actually be produced in weeks. If they respond with ridicule, walk away; if they come back curious, you have your opening, but then make sure you truly know your material. In forty-five years I have given that advice without a single qualm.