Ashton: Lord of Truth - Lonely Lords, #13

Ashton Fenwick was raised to be the bastard older brother--the charming, happy bastard older brother. Now, an earldom has been foisted upon him, and his family urgently needs him to find and marry the right countess. With charm at the ready, Ashton is prepared to go wife-hunting during the London social Season, but it's the forthright landlady at Ashton's lodging house who catches his eye. Matilda Bryce bakes delicious apple tarts and does not suffer titled fools, even as she looks after street urchins and does what she can to help Ashton prepare for the challenges before him.
Ashton soon realizes that somebody is out to destroy Matilda's happiness, and if he offers to make an honest countess of her, she could well flee. He's found the woman for him, though, and will risk all to free Matilda from her past.