Mauricio Pochettino's Spurs have safely progressed to the Round of 16 of Europe's second tier club competition courtesy of a 4-1 aggregate win over Paulo Sousa's Viola who knocked the London club out at the same stage last season.
The opening goal came on 25 minutes when Ryan Mason edged Spurs ahead 2-1 overall following last week's 1-1 draw in Florence.
Without star striker Harry Kane, Pochettino gave Nacer Chadli a chance and the Belgian through he had double his side's lead early in the second half only to be flagged offside after finishing Erik Lamela's through ball.
Sousa's outfit had managed to get a footing in the contest but were inefficient in the final third and it proved costly as down the other end in the 63rd minute, the home side went two up on the night.
Chadli's initial effort was swatted away by Tatarusanu with the ball falling to Alli who saw his toe-poked attempt blocked into the path of Lamela who had his back to goal but was able to turn and fire home for his sixth goal in the competition.
That goal eased the pressure on Spurs and allowed them to play with more freedom in the final 25 minutes which prompted them tom wrap up proceedings in the 81st minute.
Kieran Trippier's firm cross from the right was destined for a back-post touch for Alli only for Gonzalo Rodriguez's intervention to see the ball rocket in off the underside of the bar.
The result will only boost the confidence of Tottenham who now set their sights on the weekend's Premier League clash with Swansea City as they look to go top of the table.
2015/16 EUROPA LEAGUE - Round of 32 first leg