In a large microwave-safe bowl, whisk together the sugar and eggs until smooth and thoroughly combined. Whisk in lemon juice, lemon zest and butter.
Cook in the microwave for 3-5 minutes on full power, in one minute intervals, stirring after each. The cooking time will vary depending on the strength of your microwave. You will know the lemon curd is done cooking when it coats the back of a metal spoon.
Remove from the microwave and push the curd through a fine mesh sieve, then pour into a sterile jar.