01 - In a heatproof mixing bowl, whisk together eggs and granulated sugar until the mixture is uniform and pale.
02 - Incorporate the lemon zest and strained lemon juice into the egg-sugar mixture, whisking to blend.
03 - Position the bowl over a saucepan filled with gently simmering water, ensuring the bottom of the bowl does not touch the water.
04 - Continuously whisk the mixture over the simmering water until it thickens to a custard-like consistency and coats the back of a spoon, approximately 8 to 10 minutes.
05 - Remove the bowl from heat and immediately add butter cubes, whisking until fully melted and mixture is glossy and smooth.
06 - Pour the curd through a fine-mesh sieve into a clean bowl to ensure a velvety texture. Allow to cool slightly.
07 - Transfer the cooled lemon curd into sterilized jars. Store in the refrigerator for up to two weeks.