In a large bowl or stand mixer fitted with a paddle attachment, cream the butter, sugars, and vanilla until light and fluffy. Add in the egg and then slowly add the flour and baking powder to the dough in batches and continue mixing the dough until all of the ingredients are well combined.
Divide the dough into two separate bowls, ⅓ dough in one bowl, and ⅔ dough into the other bowl. To the larger amount of dough, add a few drops of green food coloring and stir until it is a bright green. Add in a few red drops of color into the smaller amount of dough in the other bowl and mix. (You can use fewer drops for a more pink looking heart).
Cover and refrigerate the dough for about 30 minutes.
Remove the green dough once it has been chilled. On a lightly floured surface, roll the dough to be about ¼-inch in thickness. Cut the dough using a large heart-shaped cutter and place the cutouts on a parchment paper-lined cookie sheet. Once done, use the small heart-shaped cutter and cut out the center of each green cookie, and set the cutout aside.
Before rolling out the red dough, preheat the oven to 375°F.
Remove the red dough from being chilled, and roll out in the same thickness as the green dough. Use the same smaller heart-shaped cutter, and cut the dough into hearts. Place them into the empty sections of the larger cookies and gently press the edges together so they will bake together.
Bake for 8 to 10 minutes, removing just as the cookies begin to turn golden on the edges. Let the cookies cool before serving.