In a microwave oven on the "defrost setting" melt the butter until it separates (usually about 3 to 5 minutes). The golden, oil-like substance (which rises to the top) is called "clarified butter" and it will be the vast majority (about 85% of the volume). With a ladle or spoon, skim off that and save it to make your Hollandaise Sauce. The remaining milky substance which sinks to the bottom is water and milk solids. You can throw that away.
Choose a small to medium size saucepan and a mixing bowl that nests within the saucepan leaving at least an inch space from the bottom and an inch or so lip at the top so you can easily lift the bowl in and out of the pan as you make your sauce.
Put a half inch of water in your saucepan and bring it to a simmer.
Place your egg yolks and 2 Tbsp. water in the mixing bowl and then place the mixing bowl over the saucepan of simmering water.
Begin whisking the egg yolk mixture and remove the bowl off of the saucepan every 15 to 20 seconds as you begin to cook your egg mixture to ensure it does not cook too fast. This will prevent your mixture from turning into scrambled eggs.
You'll know when the egg mixture is sufficiently cooked as the whisk will create tracks in the mixture. This will let you know it's time to remove it entirely from the heat and begin to add your clarified butter and lemon juice.
Begin adding the clarified butter in very small amounts by drizzling in the clarified butter. One tablespoon at a time in a thin, small stream, don't dump it in all at once. Once that is incorporated, add another, the same way.
After the 3rd tablespoon, you'll notice the mixture is getting thicker. Now is when you begin to whisk in a bit of your squeezed lemon juice...about a teaspoon.
Continue alternating butter and lemon juice until they are both used up.
Now, all you have to do is add a few dashes of Tabasco sauce and salt to taste.
If you like Bernaise Sauce, which is a derivative of Hollandaise, omit the Tabasco and simply add the following which needs to be simmered slowly, in a saucepan, over medium heat until it is reduced to nearly a paste.