Cream butter and sugar together for about 2 minutes with an electric mixer.
Add Jello and continue to mix for 1-2 minutes.
Add eggs and mix well.
Mix flour, baking powder and salt together in a separate bowl and then add to the Jello mixture. Mix just until thoroughly combined.
If rolling into ball, scoop the dough out by tablespoons and roll into smooth balls. Place on prepared cookie sheet. Spray the bottom of a measuring cup with cooking spray and then press the measuring cup onto a plate with a thin layer of sugar on it. Press each cookie ball with the bottom of the measuring cup, dipping into the sugar in between each cookie.
If making cut-out cookies, chill the dough for at least 2 hours. Divide in half and roll out each half to about 1/4" thick. Cut out shapes and place on a prepared cookie sheet.
Bake cookies at 375° for 8-9 minutes.
Let cool and then add frosting if desired.