In a standup mixer or bowl, cream together the butter and sugar until mixed.
Add the eggs, salt, vanilla, Einkorn flour, and baking soda to the mixer and on low speed. Mix until it is well incorporated and the mixture comes together. Do not over mix.
Form the dough into a ball and, with a knife, cut into two even pieces.
Place one part of the dough back into the mixer and add the bottle of dye onto the dough. Mix on low speed till the dough is colored evenly.
Cover each dough in plastic wrap and chill for at least 30 minutes, or up to a day, to let the dough firm.
Place one of the doughs on a piece of wax paper or parchment paper or even a silcone mat works great. Roll the dough into a 6 x 12 rectangle. On another piece of parchment roll out the other dough into a 6 x 12 rectangle.
Flip one dough onto the other peeling off the parchment paper on top. Carefully flip the dough onto the other dough so they are sandwiched together. Trim the edges so the two sheets of dough line up. Peel away the remaining paper from the dough.
Using the parchment to get started, roll the dough into a log. Cover with plastic wrap and chill for at least 30 minutes, or up to a day, to let the dough firm.
Remove the chilled dough from the fridge. The bottom of the dough will be slightly flat from where it was resting in the fridge. To smooth this out, gently roll the log against the counter with your hands until the edges are smooth again.
preheat oven to 350℉
Slice the dough into slices, 1/4 to 1/2-inch thick. Place them the baking sheet about an inch apart.
Bake on a parchment-papered cookie sheet for 10-12 minutes. The cookies will be really soft so let cool, and then transfer them to a wire rack.
Repeat with slicing and baking the remaining dough. Store in an airtight container for up to 3 days.