I think is incredibly hot a woman who swallows. Let a guy cum in her mouth already is something hot, but definitely increase when swallow.
The first times I cum over my wife (gf at beginning), I cum over her tits or her body. Than, 1 month or so after we start, I asked her to cum on her face (she was on her knees finishing the job) she agreed, I started cum on her face and she suddenly open her mouth and put her tongue out and some loads gone there, she just close her mouth and swallowed. My jaw dropped instantly. She told me I was the first to cum in her mouth (she had 2 exs bf). After that episode, I started to finish a lot in her mouth and, of course, she always swallowed. She told me she loved the taste.
Few years ago, after I confessed my desires to her, when we was chatting and talking about her past she confessed me she her 2 exs had cum in her mouth too and, of course, she swallowed. She finished with "did you really believe you were the first one" "You know I love the taste" "Always loved". I almost cum when she confessed it 😅 Super hot to found that