In the bowl of food processor fitted with a metal blade, pulse the confectioner's sugar and almond flour into a fine powder, pulsing three times for 15-30 seconds. Repeat the three pulses one more time for 15-30 seconds.
Using a fine-mesh sieve, sift the sugar and flour mixture two times, slowly adding in freeze-dried raspberry powder, onto a large piece of parchment paper or into a bowl with a spout. The mixture should have a very fine powdery texture with no lumps. Once sifted, set aside.
In the bowl of a stand mixer fitted with a whisk attachment, add the egg whites and cream of tartar. Whip on medium speed (speed 4 on a KitchenAid stand mixer) until the whites and cream of tartar are combined. Then, slowly increase speed to medium high (speed 6 on a KitchenAid stand mixer), gradually adding the granulated sugar, stopping to scrape down the sides of your bowl as needed.
With the mixture still on medium high speed, slowly add a few drops of food coloring until your desired color shade is reached. Continue to whip the meringue into stiff, glossy peaks, approx. 3-5 minutes. The meringue should have the consistency of shaving cream. Be careful not to over-mix, as it can "break" your meringue; check the consistency of your meringue every few minutes by dipping the whisk into the mixture.
Once your meringue has reached proper consistency, remove the bowl from the stand mixer. Add one-third of the sifted almond flour mixture to the meringue and gently fold with a rubber spatula. Once loosely incorporated, add another one-third of the almond flour mixture and gently fold into the meringue. Add the remaining almond flour mixture, and begin deflating the batter by folding the mixture towards the center of the bowl, turning your mixing bowl each time as you fold. Repeat until the batter becomes shiny and reaches the consistency of slow-moving lava. Be careful not to over-mix; to check for the correct consistency, the batter should flow from your spatula in a slow, even ribbon without "breaking", falling into the bowl and disappearing into a smooth, glossy surface after 8-10 seconds.
Once your batter has reached proper consistency, transfer to a pastry bag fitted with a 1/4-1/2 inch round tip. Begin piping onto your parchment-lined baking sheets, gently finessing your pastry bag (do not squeeze too hard), holding the tip of the pastry bag no more than 1/2 inch above the baking sheet. Follow the stencil of the heart shapes by starting on one side of the heart, dragging it down towards the center, and then back up to the other side of the heart.
Once you've finished piping your baking sheet, gently lift your baking sheet 1/2 inch from your work surface and lightly drop or tap the baking sheet onto your work surface 1-2 times to release any air bubbles.
Let the macarons stand at room temperature until a firm skin forms on the cookie; this can take anywhere from 30-45 minutes up to 1-2 hours depending on the temperature and humidity of your kitchen. To check to see if the macarons are ready, very lightly touch the tops and sides of your macarons with your finger. If you finger does not make a dent and no batter sticks to your finger, they are ready for the oven.
**Note: While the macarons are setting at room temperature, I like to prepare my raspberry jam filling (see instructions in next section).
Once the macarons are ready for the oven, preheat the oven to 300 degrees, positioning the rack in the middle of the oven. Bake the macarons one sheet at a time, for approx. 12-14 minutes, rotating halfway through around the 7-minute mark. I found that 12 minutes gave me the perfect texture, however Sur La Table recommends anywhere from 14-16 minutes.
Carefully slide the macaron-topped parchment sheets onto a wire cooling rack and allow the macarons to cool completely before removing from the parchment paper.