The two Silver Arrows drivers were separated by only 0.081 seconds at the front of the pack with nearest pursuant Sebastian Vettel, in the leading Ferrari, seven-tenths adrift in third place.
Barely 72 hours after the death of their team's former non-executive chairman, the defending five-time champion and current series leader and his team-mate were in a class of their own on the unforgiving barrier-lined Mediterranean street circuit.
Hamilton was fastest in one minute and 11.118 seconds, his most eloquent statement since arriving in the principality and side-stepping a routine pre-event news conference on Wednesday afternoon.
Many of the mourning Mercedes' team, and others, wore black armbands or carried messages on their cars on a sombre day of hazy sunshine.
It was, as Mercedes team boss Toto Wolff had said of his fellow-Austrian before the opening session, as if the sport had just lost not only a great three-time champion and larger-than-life personality, but something of its "heart and soul."
That loss was keenly felt, but had no effect on the teams and their speed as they raced as Lauda would have wanted, led by his Mercedes men.
Behind them and Vettel, Pierre Gasly was fourth for Red Bull ahead of Alex Albon for Toro Rosso with Max Verstappen pushed down to sixth in the second Red Bull ahead of Kevin Magnussen in his Haas.
Antonio Giovinazzi was eighth ahead of his Alfa Romeo team-mate Kimi Raikkonen with Monegasque Charles Leclerc 10th in the second Ferrari in front of his home crowd.
Vettel produced the session's most notable incident when he locked up at Sainte Devote and narrowly missed hitting the barriers in the closing minutes.
By then, it was clear Mercedes were in total control as they worked towards extending their record run of five season-opening one-two finishes in Sunday's race to six.
That would rub salt into Ferrari's wounds as they struggle to keep pace with their rivals. The Italian team, for whom Lauda won two of his three titles, have not managed five one-twos in the last decade.