Step 1

Combine the lemon juice, butter, and sugar in a large saucepan.

Step 2

, Place the saucepan over medium heat on the stove and heat, stirring occasionally, until the butter has melted and the sugar has dissolved, 3 to 5 minutes.

Step 3

, Meanwhile, break the eggs into a medium heat-safe bowl and beat them briefly to mix the yolks and whites together.

Step 4

, Carefully pour about half of the hot liquid into the bowl with the eggs and whisk to incorporate; this will "temper" the eggs so they won't curdle when you combine them with the remainder of the hot liquid.

Step 5

, Pour the contents of the bowl back into the saucepan and return the pan to medium-low heat.

Step 6

, Whisking constantly, cook the curd until it thickens enough to coat the back of a spoon or spatula, 5 to 10 minutes. Use a spoon or spatula to scrape the bottom and sides of the pan occasionally to incorporate any stuck-on curd, stirring it back into the main mixture.

Step 7

, Remove the curd from the heat and pour it into a heat-safe bowl or measuring cup. If you see any small bits of cooked egg, pass the curd through a fine-mesh strainer to remove them.

Step 8

, Allow the curd to cool for 15 to 20 minutes, then stir briefly and cover the surface with a piece of plastic wrap.

Step 9

, Cool the curd at room temperature until barely warm then refrigerate until set, about 3 hours.

Step 10

, Store curd in the refrigerator for up to 3 weeks; freeze for longer storage.