01 - In a small saucepan, whisk together lemon juice, lemon zest, sugar, cornstarch, coconut cream, turmeric (if using), and salt until smooth. Place over medium heat and cook, whisking constantly, until the mixture thickens and just begins to bubble, about 3 to 4 minutes. Remove from heat, transfer to a bowl, and let cool completely. Refrigerate to thicken further before assembling.
02 - In a large mixing bowl, beat coconut oil and sugar until light and creamy. Add applesauce, lemon zest, lemon juice, and vanilla extract; mix until combined. In a separate bowl, whisk together gluten-free flour, almond flour, cornstarch, salt, and baking soda. Gradually add dry ingredients to wet ingredients and mix to form a soft dough. Divide dough in half, shape into discs, wrap in parchment, and chill for 30 minutes.
03 - Preheat oven to 350°F. Line two baking sheets with parchment paper. On a lightly floured surface, roll dough to 1/4-inch thickness. Cut into rounds about 2 inches in diameter. Place cookies on prepared baking sheets, spacing 1 inch apart. Bake for 10 to 12 minutes, or until edges are just golden. Cool completely on wire racks.
04 - Spread 1 to 2 teaspoons of chilled vegan lemon curd onto the flat side of half the cookies. Top with remaining cookies to form sandwiches. Dust with powdered sugar if desired. Store assembled cookies in an airtight container in the refrigerator for up to 3 days.