Preheat the oven to 325 F.
Fill one-third of a medium sized pot with water.
Bring the water to a simmer.
In a medium bowl add in lemon zest, juice, and eggs. Whisk.
Add the sugar and butter.
Place the bowl on top of the simmering water.
Whisk until the sugar and butter are melted.
Remove from the heat.
Place the lemon filling into the Gluten Free Tart.
Bake in the oven for about 8 to 10 minutes.
Cool and serve!