Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper.

In a large mixing bowl, cream together softened butter and sugar until light and fluffy (2-3 minutes).

Add the egg and mix on low speed until fully incorporated.

Whisk together flour, baking powder, and salt in a separate bowl, then gradually add to the wet mixture until a soft dough forms.

Divide dough into 3-4 portions and mix each with 1-2 tablespoons of Jello powder.

Chill the dough in plastic wrap for 15-20 minutes.

Roll chilled dough into balls, coat in additional sugar, and flatten slightly on baking sheets.

Bake for 8-10 minutes until edges are set and tops are crackled.

Cool cookies on sheets for 2 minutes before transferring to a wire rack.

Store in an airtight container at room temperature for up to 5 days or freeze for longer storage.