Tender is the Heart by Suzan Tisdale

Shielding herself from the cruelty and machinations of those around her, Margaret MacCallen affected an image of a cold woman—mean and vindictive. Now, married to a stranger as punishment for her ‘wickedness’, she’s torn between maintaining her emotional armor or letting her true self finally free.

Facing the aftermath of the Black Death and battling powerful clans to hold onto his own legacy, Aiden Randall agrees to marry Margaret believing it will bring peace, and possibly prosperity. Her beauty and fiery green eyes are an unexpected surprise. But the vulnerable woman hiding behind the cruel facade she has created may well be his undoing.