In The Argentine's Bed by Jennifer Lewis

It was just one "simple" mission—find out whether a winemaker in Argentina was a New York millionaire's long-lost son. But Susannah Clarke quickly learned Amado Alvarez played by his own rules. He'd give her the DNA sample she wanted—if she spent the night with him! And in a moment of madness, she'd given in, to his demand and to her own desire. Now she had to return to South America to face this compelling, sensuous man again—and to face the consequences of that one unforgotten, unforgettable night in a stranger's bed….