Emma Raducanu won on her return from injury to give Great Britain the best possible start in their bid for a first Billie Jean King Cup title.
In the opening match of Britain's first-round tie against Germany, Raducanu secured a 6-4 6-4 victory - on her sixth match point after an edgy finish - over Jule Niemeier in Malaga.
The 22-year-old was playing her first match in almost two months because of a foot injury, but produced an encouraging display in the 12-nation women's team event on her latest comeback.
With Raducanu and Boulter ranked higher than each of their singles opponents, Britain are considered the favourites to reach the quarter-finals.