This recipe is the same as doing this over the stove top.  By blending the yolks and the butter first, the butter helps coat the yolk before the lemon juice is added so there is no accidental "shocking" (i.e. cooking) of the yolk. 

In the stove top version, no double boiler is needed, but a the pan needs to be over a medium heat and continually and consistently stirred.  Too low a temperature would dry out the sauce, too hot will obviously overcook it so medium to medium high heat with the pan in one hand and a whisk in the other is best.  

1 1/2 tablespoon lemon juice (1-2 lemons)

3 egg yolks

1/2 cup butter, very softened

1) Whisk all egg yolks with butter until very smooth and completely combined. Colour should be one shade lighter. *Must be thoroughly mixed before step 2 or yolks will curdle.*

2) Slowly add lemon juice and continue whisking until combined.

3) Put in microwave and zap in 10-15 second intervals, whisk and repeat until mixture is just thickened and can lightly coat the back of a spoon. 

4) Add salt and pepper to taste and sieve if a smooth sauce is desired.

Note:

* sauce will be lumpy the first 2 zappings but just whisk lightly and continue. It should work itself out.

* I usually zap total of 45 seconds up to 1 minute depending on the microwave.

Variations:

Herbed Hollandaise: finely chopped fresh leafy herbs such as basil and chives and whisk into finished sauce. Let sit to combine.