Arsenal raced into a 3-0 lead after 35 minutes through goals from Emile Smith Rowe, Pierre-Emerick Aubameyang and Bukayo Saka, as they cut through Spurs' midfield and exploited their statuesque defence at will.
Nuno introduced Oliver Skipp and Emerson Royal at the break and Spurs improved, with Heung-min Son scoring a consolation goal and Lucas Moura striking the crossbar late on.
But the manager admitted he was to blame for a third straight derby defeat in the top-flight, which leaves him under pressure after just six League games in charge.
“A lot of things went wrong , starting with decisions that I made,” Nuno said.
“The game plan didn’t work out. I’m very honest. If the game plan didn’t work out the way you wanted it to work out, it’s because you didn’t decide it well.
“I decided bad, didn’t make the right decisions. And I refuse to go much further than that. It’s my responsibility. All I have to say, I’ll say it to the players among us. Because us [we] must solve the problem.
“First of all we have to recover mentally and physically for the next one. Then we have to make better decisions, work harder and find the right decision. We started very well with a clear idea and we lost it.
"We must assume [responsibility] and realise we lost it. It is taking us too much time to go back to the things we want to do and the things we want to become as a team. We want to be a team that is fast, stronger, solid, dominant. We are not being that team.
“This is how me and my coaching staff work. First recover the players mentally and physically, help them find the right solutions for them to develop better the way we want to play football.
“We've been in football too long to realise that the positives from a second half in this game are almost lost. This thought that if we achieve a goal early in the second half maybe we then can react and go for it. It didn't happen, but all the positives are very fragile in terms of analysis that we should do.”
Despite a rudderless first-half display, Nuno refused to criticise his players in public and promised supporters Spurs would work hard to improve, with Aston Villa the visitors to north London next weekend after a Europa Conference League group match at home to Mura of Slovenia on Thursday.
“I will not judge my players in front of you [the media],” Nuno said. “I refuse to do that.
“Of course, I have a message [for supporters]. A message that we’re disappointed because today was a special game for all of us, for our fans, and we didn’t achieve the standards that our fans deserve.
“So my message is I promise we’ll try to fix it. The only message we can say by words. After that it’s work. What I expect, what I want is a totally different game in the next one.”