I’m afraid I’m going to say nothing is as yummy as homemade and is pretty quick in a microwave. Here’s my recipe; it will make 2 jars of utter heaven and keeps in the fridge for a couple of weeks:
225g castor sugar, finely grated rind and juice of 3 lemons, 100g of butter, 3 whole eggs or 4 yolks (I find the latter a bit too rich and the whites thicken it quicker)
Sieve the eggs (I put a sieve over a jug/bowl and give the eggs a quick whisk) leave to drain through whilst you prepare everything else.
Put the butter, sugar, zest and juice in a microwaveable bowl and microwave til the butter is melted and the sugar dissolved. Keep stirring every 30 seconds or so.
Once done add the sieved eggs, whisking as you do, then back into the microwave for 30 second bursts, whisking between each one until it’s the consistency of pouring custard. Put into jars, allow to cool, then into the fridge. It will thicken up as it cools.
If you want it more lemony, mash the zest and sugar together to release the oils from the zest before adding the juice and butter.
It sounds a faff, but really isn’t, and takes perhaps 15 minutes start to finish. Stirred into Greek yoghurt is nearly as good as on toast (no butter needed).