I'm trying to find this yaoi manga with a blond uke and black-haired seme who is in a suit...

Was the seme the only one wearing a suit on the cover? And was it a japanese manga or a webtoon?

Try with these but there's probably a lot more that fit your description
http://www.mangago.me/read-manga/saezuru_tori_wa_habatakanai/
http://www.mangago.me/read-manga/joou_to_shitateya/
http://www.mangago.me/read-manga/on_or_off/
http://www.mangago.me/read-manga/shinai_naru_omega_e/
http://www.mangago.me/read-manga/the_new_employee/
http://www.mangago.me/read-manga/boku_no_kareshi_no_sukinahito/
http://www.mangago.me/read-manga/my_suha/
http://www.mangago.me/read-manga/neon_sign_amber/

Thanks!! It's the joou to shitateya one.

I got the uke messed up haha