It marked the biggest result of Korpatsch's career as the German made up for the disappointment of losing the Andalucia Open final to Mayar Sherif in April.
She was made to work for it by Tomova, however, who raced into a 3-0 lead in the first set. Korpatsch fought back and saved two set points at 5-4 down before winning a tiebreak to claim the first set.
The balance shifted in the second set when Korpatsch went 3-0 up herself but then spurned the chance to serve out the match at 5-4 up, losing a tiebreak as Tomova showed her mettle.
But the Bulgarian crumbled in the deciding set as Korpatsch cruised to victory.