Short answer: "Blond" for men. "Blonde" for women. And to be clear, both words ("blond" and "blonde") are pronounced the same. Long answer: This word comes from French. For whatever reason, this noun kept its gender (that is not true for all words that come from French). You will see "blond" used for both men and women.

Thanks, Cameron. Very clear and helpful.

I am happy to be corrected but I would have said that used as an adjective in this way it never carries an e. She has straight blond hair. But with nouns it becomes gendered. He is a tall blond. She is a tall blonde.