Whisk the eggs, sugar, lemon juice, and zest together in a heat-safe glass bowl or the top of a double boiler.
Bring a pot of water to a boil and place the bowl over the boiling water (be sure the bottom of the bowl doesn't touch the water! Pour some out if this is the case). I put a wooden spoon between the pot and the bowl to allow some air to escape.
Add in the coconut milk and whisk constantly until mixture has thickened and you can pass a wooden spoon through it and it sticks a bit. Mine has taken anywhere from 10-20 minutes to form. Don't stop whisking!
Once it has thickened to your liking, carefully remove from heat and whisk the butter in, one cube at a time. Take your time and really whisk it well!
Pour the curd into the fully cooled tart crust and place in the fridge for at least an hour.
Serve with lavender infused whipped cream or just on it's own!