Playing against a Zambia side consisting of 10 of the 11 which had won the competition in Gabon and Equatorial Guinea last year, Ethiopia started in impressive fashion and came agonizingly close to scoring.
Ahmed Said raced through on goal and lifted the ball over the on rushing Kennedy Mweene but the ball somehow bounced over the crossbar.
Buoyed by a vociferous following, Ethiopia continued to threaten and had the perfect opportunity to take the lead on 23 minutes when Said was fouled inside the penalty area by Lungu.
But the striker appeared to lose his nerve at the crucial moment as his effort was easily dealt with by Mweene.
That miss looked to have taken the momentum out of Ethiopia's sails and it was left firmly on the back foot 12 minuets later as Tassew was shown a straight red card after taking out Lungu in dangerous fashion.
He told reporters: "First of all I would like to congratulate Ethiopia for a very good performance.
"I'm not surprised -- I said be careful of this team, they are able to play very good football.
"Today, we have to thank our goalkeeper -- without Kennedy Mweene it could have been a very, very bad result.
"Our fans expected more than we did today, and they are right. Today, it was the fault of the coach. I did not prepare the team well to start the competition -- we'll see how things go after the third game.
In Group C's other game, Nigeria conceded a 94th minute equalizer as Burkina Faso grabbed a 1-1 draw.
Emmanuel Emenike's 22nd minute strike had put the Super Eagles ahead and it looked on course for victory until defender Efe Ambrose was shown a second yellow card with 16 minutes remaining.
And with just seconds remaining, Alain Traore rounded off a a wonderful counter-attack to steal a point and leave Nigeria stunned.
"All four teams have one point so everything is open," Burkina Faso coach Paul Put told reporters.
"The performance today showed who Burkina are -- we have quality in the team.
"We were missing some key players so I am very proud of what we did. I was confident of getting a point against Nigeria.
"This was a very good result for us and I am looking forward to the second game against Ethiopia."
Nigeria coach Stephen Keshi, who won the competition as a player in 1994, insists the disappointing of failing to close out the game will not affect his players.
He told reporters: "I am not going to let anything bring us down. I'm very proud of the boys, who did everything I wanted of them.
"This game is gone and the next game against Zambia is very, very important. I'll pick up the players and motivate them."