The Promised Heart by Paula Quinn

Like the sun, Tanon’s fire cannot be extinguished.
By the king’s order, Lady Tanon Risande has been promised to wed a fierce Welsh prince as a gesture of Norman goodwill. But the Prince Gareth ap Owain seems more like a pulsing beast ready to devour, and Tanon doubts she can obey her king and wed the untamed dragon prince. When he claims her hand in a tournament, beating dozens of men to win her, she knows he won’t leave without his promised prize, and she can’t help but fear bedding a barbarian. But like the sun, Tanon’s fire cannot be extinguished. In it, she possesses the power to subdue a king, tame a dragon, and bring peace to the wild lands of Cymru.

Gareth may be a prince, but his primal sensuality proves he’s no courtly gentleman. But he’s determined to show the woman he’s loved since he was a boy that he saves his savagery for the battlefield, not the bedchamber. He’ll use far more persuasive methods to draw his lady into his arms. But though Gareth is a prince, he can’t offer Tanon the finery she’s used to, nor can he be sure she will be safe in his untamed land of Cymru, where princes plot against princes and Marcher lords take more of their land each day.