Ryan Giggs - in his 100th Champions League game - sent Wayne Rooney clear for the best chance of a cagey first half, but Gregory Coupet saved well.
United were stunned soon after the break when Benzema turned and fired brilliantly past Edwin van der Sar.
Cristiano Ronaldo had a free-kick tipped over before Tevez blasted home.
Sir Alex Ferguson will be delighted to come away on level terms after an uncomfortable evening in France, and his team are favourites to progress from the return leg of this last-16 tie in a fortnight.
The United boss will be wary, however, of the cutting edge Lyon possess in Benzema, a man his club have been constantly linked with.