Prepare the Citrus Curd: Whisk together 1 egg, ½ cup granulated sugar, 1 tsp cornstarch, a pinch of salt, ¼ cup fresh citrus juice, and 1 tsp vanilla extract in a medium bowl until smooth. In a saucepan, melt 2 tbsp butter over medium-low heat. Gradually add the egg mixture, stirring continuously until the curd thickens (about 5-10 minutes). Strain to remove lumps, then cover and chill for at least 2 hours.

Make the Cookie Dough: In a large mixing bowl, cream together 6 tbsp of softened butter and ⅔ cup sugar until fluffy and light in color. Beat in 1 egg and 1 tsp vanilla extract until well combined. In another bowl, pulse ⅔ cup of freeze-dried fruit into a fine powder, then mix with 1¼ cups flour and ½ tsp salt. Gradually blend the dry ingredients with the wet mixture to form a soft dough.

Shape the Cookies: Preheat your oven to 350°F (175°C). Using a cookie scoop, portion out the dough into 12 even balls and place on a baking sheet lined with parchment paper. Press your thumb gently into the center of each ball to create an indent. Chill the cookie dough on the baking sheet for at least 30 minutes.

Bake the Cookies: Once the dough is chilled, place the baking sheet in the preheated oven and bake the cookies for 12 minutes or until the edges are lightly golden. Allow cookies to cool completely on a wire rack.

Fill with Curd or Jam: Once the cookies are cool, carefully spoon your chilled citrus curd into the indents of each cookie. Serve immediately or store in an airtight container for later enjoyment.