With the series revised to a one-race event for this round as the curtain raiser for the F1 Monaco Grand Prix, the 16-year-old started off in the best possible way by qualifying in pole.
But the Josef Kaufmann Racing team were then adjudged to have replaced a faulty screw with one slightly larger than allowed.
Despite no performance gain, the ADD Motorsport-supported racer was put to the back of the grid.
However, with just a few proper laps of racing due to bad weather and red flags, Lando could at least find some positives with only half points awarded at the end and the racer still topping the leaderboard.
He said: “It was really disappointing. The screw that was used was just a few mil bigger than the normal one, but it was in the rules and when it was discovered meant I was penalised.
“It was my first time racing at Monaco – and on a street track – and I topped the times in practice and qualifying, despite racing against drivers who had raced on street tracks before.
“But it was a little mistake that cost us – even though they said there was no performance gain through it.
“I raced well and could have still finished 11th, but a late crash saw them take the result back to lap six.
“We had good pace, but obviously it’s not what we had hoped for.”
Lando got his Eurocup Formula Renault 2.0 campaign off to a brilliant start last month with two wins on the opening weekend at Aragon.
Friday practice in the second round gave Lando a chance to get used to a street track for the first time, but it didn’t take him long to get into his stride as he finished fastest.
Qualifying took a different format with all drivers included in a 55-minute session rather than split into two groups.
But despite easing up over the final two laps, the Somerset racer continued in the same form to finish in pole.
After being hit with the penalty after scrutineering uncovered the ‘technical non-conformity’ and starting at the back of the grid, the race itself was then hampered by rain and safety cars.
The first two laps were behind the safety car and after the green it wasn’t long before another safety car was needed after a crash.
Lando managed to get up to 11th, but another crash ended the race early with the final positions rolled back to lap six, meaning he finished 16th.
With the race not reaching 75 per cent distance, only half points were awarded to the top ten drivers, remarkably leaving the teen top of the overall standings.
He added: “The only positive to take away from the weekend was that the leaders were only awarded half points meaning I’m still top, despite the set-back.
“But it was really cool to get the chance to race at Monaco and on a street track, I really enjoyed it. There was no room for error.
“The atmosphere was brilliant and to be part of the F1 build-up was a great experience.
“It could have been even better if I’d had the chance to race from the front, but these things happen.
“Hopefully I’ll get the chance to come back one day soon.”