Combine eggs, salt, sugar, lavender, zest, and lemon juice in a metal or glass bowl you can use as a double boiler (or bain-marie). Whisk for a couple of minutes or until the egg mixture becomes pale and combined. The mixture should be smooth. Place the bowl over a small saucepan of simmering (not hard boiling) water and continue to whisk.

When the mixture starts to warm and loosen, start adding the butter, a piece or two at a time for the first two times, whisking constantly. When all of the butter is added and incorporated, keep whisking until it thickens (about 5-10 minutes). The mixture should NEVER boil during this process!

Once thickened, remove from the heat and strain through a sieve into a storage container. You can use immediately or let it cool. If you are not using it immediately, it will keep for about two weeks in the refrigerator in an air tight container. Enjoy!