4 tbsp. butter (no substitutes), divided
3 tbsp. all-purpose flour
1 c. milk
2 egg yolks
2 tbsp. lemon juice
1/2 tsp. salt

In a 1 quart microwave safe dish, heat 2 tablespoons of butter, uncovered, on high for 30 seconds or until melted. Whisk in flour until smooth. Gradually add milk. Microwave, uncovered, on high for 1 minute; whisk lightly. Heat 1 minute longer or until thickened. Whisk in remaining butter until melted.

In a small bowl, beat egg yolks; add small amount of hot milk mixture. Return all to the 1 quart dish, stirring constantly. Whisk in the lemon juice and salt until combined. Microwave, uncovered, on high for 1-2 minutes or until a thermometer reads 160°F. Refrigerate leftovers.