Step 1

Halve 1 large lemon and remove any seeds. Juice one half until you have 1 tablespoon juice. Save the remaining lemon half in case you want to add more at the end.

Step 2

Finely chop 1 small shallot until you have 2 tablespoons and place in a small saucepan. Strip the leaves from 2 large tarragon sprigs and finely chop until you have 3 teaspoons; add 1 teaspoon to the saucepan and reserve the remaining.

Step 3

Add 1/4 cup white wine vinegar to the saucepan and bring the mixture to a boil over medium heat. Boil until the vinegar is almost evaporated, about 5 minutes. Transfer the mixture to a medium bowl and let cool slightly.

Step 4

Wipe the saucepan clean with a paper towel and add 1 1/2 sticks unsalted butter. Return to medium-low heat and heat, stirring occasionally, until fully melted. Immediately remove from the heat.

Step 5

Add 3 large egg yolks to a blender. Place the lid on the blender without the center part. With the blender running on high, very slowly pour in the melted butter. Stop the blender and add the lemon juice and 3/4 teaspoon kosher salt. Replace the center part of the lid and pulse until combined.

Step 6

Pour the sauce into the shallot mixture. Add 1 1/2 teaspoons of the tarragon, season with black pepper, and stir to combine. Taste and season with more kosher salt, black pepper, or lemon juice as needed. The sauce should be thick enough to coat a spoon, but thin enough to drizzle from the spoon. If it is too thick, thin it out with water 1/2 teaspoon water at a time. Garnish with the remaining 1/2 teaspoon tarragon and serve immediately.