Step 1

In a large bowl, whisk together the eggs, sugar, lemon juice and zest and salt until you get a smooth mixture.

Step 2

Pour the mixture into a medium saucepan and add the rosemary. Place over medium low heat (think 3 or 4 out of 10 or so). Stir constantly, using a wooden spoon, taking special care to get the "corners" of the pot so nothing sticks.

Step 3

Cook until the curd thickens, about 5-7 minutes or so. You'll know it's about ready when you can swipe through the curd on the back of the wooden spoon and it leaves a clear path (without running back together). Then turn the heat all the way to low and stir in the butter. Cook and stir until the butter is melted and fully incorporated.

Step 4

When the curd is cooked, remove the rosemary and strain the curd into a glass jar and seal it. Allow to cool on the counter to room temperature before refrigerating overnight, or at least 6 hours. This will allow the curd to fully thicken to its proper consistency.