Take a heavy bottom saucepan and add the lemon juice, lemon zest, sugar, salt and eggs. Whisk to combine everything and place it on medium heat. Keep stirring for 3 minutes as it slowly cooks and dissolves the sugar.
Reduce the heat to medium low and start adding butter cubes, 2 at a time. Keep stirring continuously and as the cubes melt, add 2 more. Continue the process till you have added all the butter cubes. In about 6 to 7 minutes, you will notice that the curd will start to thicken. You will know it’s ready when it coats the back of the spoon.
Take the pan off the heat and let it cool down a bit. It will continue to thicken as it cools. Then, strain it into a clean airtight jar. Once it cooled down completely, seal it tight and keep it in the refrigerator.