Make the Dough:

In a large mixing bowl, cream together the butter and sugar until light and fluffy (about 2–3 minutes). Beat in the egg and vanilla extract until smooth.

Add Dry Ingredients:

In a separate bowl, whisk together the flour, baking powder, and salt. Gradually mix the dry ingredients into the butter mixture until a soft dough forms.

Divide and Color:

Split the dough into 2 or 3 portions. Leave one plain, and tint the others with a small amount of red or pink food coloring. Knead gently until the color is evenly distributed.

Create the Marble Effect:

Lightly knead the colored and plain doughs together just a few times to swirl the colors. Don’t over-mix—you want a marbled look, not a uniform pink.

Chill:

Form the dough into a flat disk, wrap in plastic, and chill for at least 1 hour (or up to overnight).

Roll and Cut:

Preheat your oven to 350°F (175°C). On a lightly floured surface, roll the chilled dough to about 1/4 inch thick. Use heart-shaped cookie cutters (or any shape you like) to cut out cookies.

Bake:

Place cookies on a parchment-lined baking sheet, about 1 inch apart. Bake for 10–12 minutes, or until edges are just starting to turn golden. Don’t overbake.

Cool and Enjoy:

Allow cookies to cool on the pan for a few minutes before transferring to a wire rack. Serve as-is or drizzle with a simple icing or dust with powdered sugar.