It was the seventh top-level tour title of his career -- the last of these coming in Houston in April, 2014 -- and the fifth on claycourts.
Pouille, at 22 10 years younger than his opponent, was playing in his first ATP tour final, but he never looked like troubling the tough Spaniard, a former top tenner who has slumped to 60th in the world rankings.
The final had been held over from Sunday due to heavy rain in the Romanian capital.