Make the lemon curd ahead of time and place in refrigerator to chill.
To make the Lemon Curd:
Whisk together lemon juice, sugar free sweetener, and eggs until well combined. Place in a double boiler with a hot simmer and stir constantly until thickened, about 10 minutes. Remove from heat, add butter and lemon zest. Stir until combined and creamy. Chill until ready to use.
To Make the Cookies:
Preheat oven to 350 degrees.
In large mixing bowl, cream together cream cheese and butter. Blend in sweetener until well combined.
Add almond flour, coconut flour, salt, and vanilla extract. Mix until stiff dough forms. Measure about 3/4 tablespoon dough and shape into ball. Place on cookie sheet lined with parchment paper and put a small indent in dough with thumb.
Bake for 12-15 minutes. Remove from oven and cool completely.
When ready to serve, place 1 teaspoon lemon curd in center of cookie. Store unused lemon curd in refrigerator.
Updated 4/7/19: You can choose to use powdered or granulated swerve in the cookie dough, whatever your preference is. I have used both and have had good results every time.