In a medium bowl, thoroughly whisk together the eggs and egg yolks.
6 large eggs, 3 egg yolks
In a medium saucepan, combine lemon zest, lemon juice, honey, and cubed butter. Heat on medium heat until the butter melts and the mixture starts bubbling at the sides. Turn off the heat.
3 tablespoon zest from two or three lemons, ¾ cup fresh lemon juice, ¾ cup honey, ½ cup butter
Take about ¼ cup of the lemon mixture from the pot using a measuring cup and allow it to cool for 30 seconds. While whisking continuously, slowly drizzle this into the eggs. This step tempers the egg yolks preventing them from cooking on contact.
Slowly incorporate the remaining lemon mixture into the eggs while whisking continuously.
Pour the mixture back into the saucepan and heat on medium-low until it thickens and coats the back of a spoon.
Strain the mixture through a fine mesh strainer into the cooked oat cookie tart shell, smoothing out the top. (Reserve ⅓ cup of the lemon curd for swirling in the Greek yogurt whip later.)
Bake at 350 degrees F for 8 minutes until the edges of the lemon curd are just set.
Allow the tart to cool completely, then chill in the fridge for 2 to 3 hours or overnight.