For the cookie dough:
1 cup sugar
1 large egg
2 cups all purpose flour
1 tsp baking powder
1 tsp vanilla
1/2 tsp table salt
Preheat oven to 350 degrees.
Cream the butter and sugar together until light and fluffy. Add the egg and beat until incorporated.
Add the flour, baking powder, salt and mix well. Add the vanilla and mix until incorporated.
Divide the dough in half, wrapping the half you are not working with in plastic wrap and refrigerate.
Add Deep Pink gel food coloring to the other half and knead until well incorporated. It's a good idea to wear latex gloves to protect your hands from the food coloring. Now divide the pink and the plain dough into 8 portions about the size of a golf ball. Arrange the dough balls alternately on a well floured surface.
Knead half of the dough balls into one mass. Do not blend the colored dough too much or you will wind up with an all pink cookie. Remember rolling the dough with a rolling pin will also blend the color. You're striving for a marbled effect.
Roll the dough out on a well floured surface and cut with any size heart you like. Bake 10- 13 minutes depending on size on a baking sheet lined with parchment paper. Cool on a rack.