Blend the freeze-dried fruit to a fine powder in a food processor or spice grinder. For a quick paste filling, mix some of the powder with a teaspoon or two of water until it forms a spreadable paste.

Cream butter and granulated sugar together until light and slightly fluffy. Add egg and vanilla, and mix until combined. Stir in flour and salt until the dough forms. Fold in the freeze-dried fruit powder.

Roll dough into small balls (about 1 to 1 ½ tablespoons each) and place them on a lined baking sheet. Press a firm well into the center of each ball with your thumb or the back of a measuring spoon.

In a small saucepan, whisk egg, sugar, and cornstarch until smooth. Stir in lime or lemon juice, vanilla extract, salt, and lime zest. Cook over low heat, stirring constantly, until thickened. Remove from heat and stir in butter until smooth.

Preheat oven to 350°F (175°C). Bake cookies for 10–12 minutes until edges are lightly golden. Press the centers again if needed to reform wells, and fill each with fruit paste or lime curd.

Let filled cookies cool on a wire rack. Store baked cookies in an airtight container at room temperature for up to 3 days, and lime curd in the fridge for 4-5 days.