Nadal is expected to now partner Marcel Granollers against Britain's Jamie Murray and Neal Skupski in the crucial third rubber which will decide who reaches the showpiece final on Sunday.
ATP Monte Carlo
Medvedev withdraws from Monte Carlo after testing positive for Covid-19
He had no trouble beating Evans after a tight few games early on in the opening set, and the world number one really stepped up his intensity in the second.
The 19-time Grand Slam champion was roared on by a vociferous home crowd and he made it count in style by not losing a single game after the opener.
Nadal delivered a stunning bagel to close out victory with Evans not afforded a glimmer of an opportunity.
The home fans were delirious as Nadal clinched the win and quickly strode off court to likely play in the doubles rubber which will decide the semi-final.
Britain, who won the Davis Cup in 2015, are competing in their third semi-final in five years.
The winner of the tie will take on Canada in Sunday's final in Madrid.
Highlights: Del Potro beats Nadal in astonishing semi-final at Rio 2016
'There's nothing I like about clay' - Medvedev not looking forward to French Open