If you want to use coconut oil instead of butter choose a refined version to reduce the flavor of coconut.If you'd like to can the curd, add the curd to clean, hot jars, leaving about half an inch of space at the top. Remove any air bubbles and place the canning lids on the jars. Let cool undisturbed for 12 to 24 hours.To freeze the curd, let it cool for a bit in a clean container with a seal and then freeze.
Set up a double boiler: fill the saucepan about a third of the way with water and bring it to a boil, then lower it to a simmer.
In a bowl that fits on top of the saucepan without touching the bottom, add the egg yolks, lemon juice, zest, honey, and salt and whisk to blend well.
Place the bowl on top of the saucepan with the simmering water and whisk the egg mixture for about 10 minutes or so until it thickens. Cook slowly and gently whisk continuously. Keep whisking to prevent the eggs from curdling. Turn up the heat a bit if it's not thickening.
Take the curd off the heat, add the butter and whisk to combine it with the curd. Once the butter is melted cover the curd with plastic wrap to prevent a skin from developing on top.
Cool and then store covered it in the refrigerator for a few weeks. See notes if you'd like to freeze it or can it.