Wash and dry the lemons. Then zest and juice them. You need about 1 tbsp of zest and 1/2 cup of lemon juice. Or leave the zest out completely.
In a medium pot, add the eggs. I use three full eggs and an additional egg yolk. Whisk for about a minute or so.
Add in the sugar and whisk for another minute or two. Follow that up with the lemon juice and lemon zest. Whisk until well combined.
Place the pot on the burner and set the heat to medium-low. Continuously stir and whisk the mixture until it thickens. About 8 to 12 minutes. It is done when it clings to the back of a spoon. The temp will be right around 170F or a little hotter.
Once it thickens remove it from the heat and add in the butter. Stir until the butter has melted.
Pour the warm lemon curd into a strainer over a bowl, this will leave behind any larger bits of zest that you may not want in your curd. This is an optional step.
Cover the bowl/container with plastic wrap. Make sure the plastic touches the top of the curd. Then chill in the fridge for about 1 hour. Eat it as is or spread it on toast, scones, biscuits, etc. It can be used as a filling for cupcakes, cakes, tarts and combined with whipped cream for pastry cream for cream puffs, eclairs, and donuts. Enjoy!