The suit is kind of technical, but the long story short ... Eva's accused of lending $1 mil to the company behind Beso ... with the agreement that she'd get paid back at an astronomical amount of interest ... racking up $4.6 million over 2 years.
The person who filed the lawsuit today in L.A. County Superior Court, an investor named Mali Nachum, claims Eva's deal not only violates California law -- but it cuts into his percent of the company.
Mali wants more than $4 mil in damages.
UPDATE: A rep for Longoria tells TMZ, "This is a desperate reaction in a lawsuit without merit by prior partners who, through their unauthorized and fraudulent actions, required Eva Longoria to seek reorganization protection through bankruptcy court in Nevada."