Cream butter, sugars, eggs, and vanilla until combined.
Slowly add flour, salt, and baking powder.
Do not be afraid to use your hands to really get the dough blended.
Split dough into thirds.
Set one aside and separate the remaining two into separate bowls.
Add red food coloring to one of the dough mixtures and use an electric mixer to adequately tint the dough.
Repeat with the other third and blue food coloring.
Roll out each color into a rectangle on wax paper as shown above.
Layer the three colors of dough and refrigerate at least two hours.
When ready, slice cookies and place on parchment paper on cookie sheet.
Bake at 375 • for 9-11 minutes.
Let cool completely before moving.