Got a few suggestions, though 'crossdress' can mean a few different things. I'm thinking of those stories where a character has to convincingly live as another gender, often for survival or a mission, and romance gets tangled in the deception. The classic for me is the Chinese web novel 'The Disguised Male Queen' by Xiao Ya. It's a wild ride set in a fictional esports/gaming world where the female lead has to pretend to be a man to join a pro team. The romance with the team captain is a masterclass in slow-burn tension. Every accidental touch, every shared moment feels charged because of the secret hanging between them. The author really digs into the psychological strain of the disguise and the fear of rejection.
If you're open to manga, 'Hana-Kimi' is an oldie but a goodie. A girl disguises herself to attend an all-boys school to be near her track idol. The romance is sweet and filled with near-misses and dorm room chaos. The subplot with the doctor character, Umeda, actually has more interesting romantic tension than the main couple, in my opinion. His awareness of her secret and his protective, slightly world-weary dynamic with her adds a whole other layer.
For something with more political intrigue, check out 'The King's Beast' by Rei Toma. It's not strictly crossdressing, but the female protagonist serves as a male-attired palace guard, creating a power imbalance and forbidden love angle with the prince she's sworn to protect. The art is gorgeous, and the romantic subplot simmers with a gothic, tragic feel.