Beat butter and sugar at medium speed with an electric mixer until blended.
Add eggs, one at a time, beating just until blended after each addition. Gradually add the lemon juice to the butter mixture, beating at low speed just until blended after each addition; stir in zest. (Mixture will look curdled). Transfer to a 3 quart microwave safe bowl.
Microwave at High for 5 minutes, stirring at 1 minute intervals. Microwave, stirring at 30 second intervals, 1 to 2 minutes longer or until the mixture thickens and coats the back of a spoon, and starts to mound slightly when stirred.
Place heavy duty plastic wrap directly on the warm curd (to prevent a film from forming) and chill for 4 hours or until firm. Store in an airtight container in the refrigerator for up to 2 weeks.