Cut butter into four pieces and place in 1-quart glass bowl. Cover with a paper towel and microwave on high until almost melted, 45 seconds to 1 minute. Remove from microwave and stir until completely melted.
Separate eggs. Beat yolks well with whisk or fork, then stir into melted butter. Add cream and 1 tablespoon lemon juice to egg mixture. Stir well.
Microwave uncovered mixture on high until just slightly thick, 1-2 minutes, stopping every 20 seconds to stir with whisk or fork. Remove from microwave and stir in extra lemon juice if desired.
This process heats the egg yolks, meaning they're not raw and are safe to consume during pregnancy.