Use a cookie cutter or a heart shaped template to make the heart shapes on a parchment lined baking sheet. Leave at least 1 inch of space between each macaron. (If using an oven safe template, place under the parchment)
Pour the almond flour into a food processor and grind until it becomes like a fine powder.
Next, add the almond flour to a sieve with the powdered sugar. Sift together into a medium mixing bowl. Repeat this process two more times (for 3 times total) discarding any large pieces that don't fully sift through the sieve. Set aside. (Pro Tip: The more you do this step the glossier the top of the macaron will be.)
In the large bowl use an electric mixer to beat the egg whites until frothy, about 5 minutes. Add the cream of tartar and salt, beating for 1 minute on high speed.
To the egg whites, add vanilla and 4-5 drops of the food coloring. (Adjust the intensity of the color to your liking) Beat to combine. Gradually add the granulated sugar to the egg white mixture beating on high speed until it's a light and fluffy stable meringue and stiff peaks form.
Slowly add the sifted dry ingredients to the egg white mixture 1/3 at a time. Fold into the meringue by hand using a rubber spatula. Repeat until all is added. (You can also do this using the mixer on medium speed. Be careful to avoid deflating the meringue.)
Transfer the batter to a piping bag. Fill each heart shape evenly with cookie batter.
Tap the cookie sheet on a counter gently to release any air bubbles. Let stand for 30-40 minutes to dry or until a skin forms. (This step helps avoid cracks in the macaron shells.)
Bake: Preheat the oven temperature to 300°F. Bake macarons on middle rack for 7 minutes. Rotate the pan and continue baking for another 5 minutes. The cookies should be just slightly toasted on the edges.
Remove from the oven and let cool on the baking sheet for 5-10 minutes then carefully remove to a cooling rack to cool completely.
Make the Buttercream Macaron Filling: Using an electric mixer in a medium bowl beat the softened butter with vanilla extract until fluffy. Gradually add powdered sugar then add cream (or milk) 1 Tablespoon at a time until desired consistency is reached. (It should be thick not runny.)
Transfer to a pastry bag (OR use an icing spatula) pipe buttercream onto one cookie, placing another on top to form the cookie sandwich.
DIY Heart Shaped Macaron Template: Use a heart shaped cookie cutter to make indentations on parchment paper then place onto the sheet pan and follow the lines when piping the macaron batter. You can also use the tip of a knife to outline the cookie cutter, allowing at least 1- inch between each macaron for baking. This will help keep them uniform in shape.