1cupfreshly squeezed lemon juice(about 3-5 lemons, strained to remove pulp and seeds)
zest from 2 lemons(zest lemons before squeezing!)
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Melt butter in a small pot over low heat (note 1).
In a mixing bowl, beat the eggs until bright and foamy (note 2).
Add the lemon juice, sugar and lemon zest to the butter and stir in the beaten eggs while whisking
Over medium heat, gently heat the mixture while stirring constantly. Don't bring to a boil. If you have a thermometer try to stay between 185°F to 195°F (note 3).
After about 10 minutes, the curd will start to thicken. Keep on simmering, while stirring, until it has the consistency of a thick sauce.
Pour into clean containers and let cool. Store in refrigerator for up to one week. It will continue to thicken as it cools.
Use stainless steel or enameled materials. Aluminum can cause a metallic aftertaste when it reacts with the lemon. Also try to use a silicon or plastic whisk and spoon instead of metal.
Beating the eggs until foaming is mainly to get a smooth consistency but also contributes to color. If you just beat the eggs with a fork, you can add it to the mixture through a sieve. The lemon curd will look a bit darker/more orange.
If the mixture gets too hot it can curdle. If this happens, don’t worry, it's not lost. You can use an immersion blender to blend everything back together. Let come to room temperature and then place in the fridge.
Don't overcook it, it can cause the curd to become gel-like. This is only a visual problem though, it will still taste good.
Storage: Store in airtight container in the fridge for up to a week. Lemon curd freezes well. Use small containers or ice cube trays to portion it out, if desired.