I've been skimming lots of romance books lately, but Birthday Girl was the only one I finished and enjoyed. He did have the supportive and gentlemanly traits I wanted in an older love interest.

Seeking recommendations for older hero that is a gentleman, speaks like a mature older person and patient with the heroine, maybe slow burn (but not too slow - Birthday Girl was a bit fast but around that pace is fine) with an age gap. No absuive or toxic shenanigans, looking for something wholesome, contemporary, hero is not a jerk or arrogant towards her, so probably not enemies to lovers here. I wince a little at heros that can be described as "true alpha-male billionaire" or "brooding" but if they hit all the other boxes most of the time, I'd give it a try.

I also really liked the scenes where she worked with him at the sandbagging etc, those daily bonding moments that aren't focused on each other but bring the both into the same orbit.

Contemporary preferred but historical settings is fine as long as it's evident he's older/age gap issues they have to sort out or accept. Age gap romance without veering into unhealthy relationship or complete boredom. I did sift through previous threads that asked for similar recs to Birthday Girl but many I skimmed had the age gap I liked but the hero or toxic relationship dynamics or dark or fantasy settings (mafia/vampires) that I wasn't particularly interested in.

Adding other reads that I chanced upon:

Absinthe by Winter Renshaw