Kartal looked at GB’s triumph against France during last year’s qualifications from afar, after spending three months with a health problem.
However, it has increased the ranking in the past 12 months, winning its first WTA title on the way.
A good engine on clay, she played with confidence in a first set which saw seven service breaks in 10 games, adapting well to the rhythm of Niemeier.
Kartal was used at the opening of 5-3 but was broken, before two double defects from Niemeier put the Briton.
Niemeier of Germany, heavily beaten against the Netherlands and fighting for the form, covered the face of his towel at the end of the whole when it was visibly upset.
Kartal won five consecutive games to lead Niemeier by a set and a break, redirecting the rhythm of the German around the field, before winning the victory.
“I’m super proud of this first game,” said Kartal.
“It’s obviously scary when you are the first game, but I’m proud of my performance.”
