The Passionate Heart by Paula Quinn

Norman Lord Brand Risande, known as “The Passionate” is temptation incarnate with the power to pull and lure, and cause kingdoms to fall. But he hides a bitter secret; the betrayal that has sealed his heart. Now as this most feared warrior rides out to possess the lands he has won in war, he engages his most formidable enemy ever.
Saxon Lady Brynnafar Dumont is prepared to do anything to protect her people—even seduce the savage knight who defeated her father. But instead of a cold-blooded beast, she confronts a purely sensual scoundrel who wants nothing to do with her.