Third seed Simona Halep remains on course to defend her title at the Madrid Open.
The Romanian was given a scare by Roberta Vinci earlier in the tournament but was in prime form in her quarter-final on Thursday.
She swept past American Coco Vandeweghe 6-1 6-1 in just under an hour, breaking five times and not losing her own serve.
Halep will now face Latvian Anastasija Sevastova in Friday's semi-finals after the World No 22 saw off Kiki Bertens 6-3 6-3.
Eugenie Bouchard had been impressive in reaching the last eight but she was no match for Svetlana Kuznetsova, who powered to a 6-4 6-0 victory.
The Russian will next face France's Kristina Mladenovic, who beat Sorana Cirstea 6-4 6-4.