It was the 23rd career WTA title for the two-time Wimbledon champion.
Kvitova broke Buzarnescu in the fourth game of the deciding set and held her serve for a 4-1 lead. The 10th-ranked Czech converted her first match point on clay on the way to her third title this year after wins at St. Petersburg and Qatar.
Buzarnescu, who played her second final this year, has yet to win a tournament.
Struggling with her serve, Kvitova lost her first set in the tournament after serving five double-faults.