Diego Fabbrini's early opener preceded the Spaniard's brace as last season's play-off finalists, who began the campaign with an uninspiring goalless draw at Preston, put in a stylish performance back in front of their own supporters.
Anticipation was high on Teesside, especially with Middlesbrough-born Stewart Downing making a second home debut for the club following his surprise switch from West Ham.
But it was another of Aitor Karanka's summer recruits who put Boro ahead, Watford loanee Fabbrini producing a spectacular long-range strike after seven minutes.
That paved the way for a rampant first 45 minutes, with Middlesbrough entering the break 3-0 ahead as Kike twice converted from close range.
The win leaves Boro second in the table, two points behind early pacesetters Brighton.
Albion are currently the only team with maximum points from two matches after Tomer Hemed's penalty deep into injury-time gave them a 2-1 win at Fulham.
Sam Baldock put the visitors ahead but Tom Cairney quickly equalised before Hemed held his nerve from the spot after Shaun Hutchinson had fouled Kazenga LuaLua.
The highest-scoring game of the day was at Ashton Gate where Bristol City were beaten 4-2 by Brentford.
City twice led through goals from Jonathan Kodjia and Aaron Wilbraham but Alan Judge and a Derrick Williams own goal brought the visitors level
In between those Brentford goals, City forward Luke Freeman was shown a straight red card for a high challenge on Harlee Dean and in the s econd half the extra man counted as strikes from Hull target Andre Gray and Philipp Hofmann gave Marinus Dijkhuizen his first win as Bees boss
Paul Clement is still looking for his first victory in charge of Derby as their stuttering start continued with a 1-1 draw at home to Charlton
Tony Watt put the Addicks ahead before Chris Martin equalised
It was also 1-1 at the John Smith's Stadium between Huddersfield and Blackburn as Nathan Delfouneso cancelled out Nahki Wells' opener for the hosts
Nottingham Forest got off the mark with a 2-1 home victory against Rotherham, who prop up the table at this early stage following back-to-back defeats
Danny Collins opened the scoring against his former club but the Reds replied through Matt Mills and the much sought-after Michail Antonio, who already has three goals this season
It was the same score at Portman Road as Tommy Smith and Freddie Sears turned the match around for Ipswich after Ross Wallace had put Sheffield Wednesday ahead
Paul Gallagher's first-half strike settled the game between two of last season's promoted teams as Preston, who had Jordan Hugill sent off for violent conduct seven minutes from time, won 1-0 at MK Dons
In the lunchtime kick-off, Burnley drew 2-2 with Birmingham
Jon Toral and Paul Caddis had the Blues twice ahead at Turf Moor but the hosts levelled on each occasion with goals from Michael Keane and Matthew Taylor
Source : PA
Source: PA