Line two baking sheets with parchment paper or silicon mats (I use silicon mats)
Combine the powdered sugar, almond flour, and peanut butter powder in a food processor fitted with the blade attachment. Blend to work out any lumps in the almond flour and to grind to a fine powder. (You can skip this step if you don't have a food processor. I didn't have one for a long time and my macarons still tasted good, they just didn't look as pretty)
Place the egg whites in a large bowl and beat until they start to form foamy bubbles (about 30 seconds). Add the cream of tartar and beat another 30 seconds to mix.
Add the sugar to the egg whites, one tablespoon at a time, beating for about 30 seconds after each addition to help the sugar dissolve.
Continue beating the egg whites until just about stiff peaks stage.
Sift the powdered sugar mixture over the egg whites (Lazy cook tip-I often skip this step and the macarons are fine to me, they just don't come out as pretty). Then gently fold the sugar mixture into the egg whites with a spatula. Be really careful here not to knock out the air you whipped into the egg whites. Whenever I'm folding dry ingredients into wet ones I hear Paul Hollywood's voice mimicking Mary Berry on GBBO's Masterclass: "Around the outside, then cut through the middle!"
Fill a piping bag with a wide tip with the macaron batter, then pipe quarter-sized rounds onto the prepared baking sheets. If your macarons have little tails from the piping, wet your fingertip with water and gently press them back into the cookie.
Drop each pan on the counter 2-3 times from a few inches above the surface of the counter. This helps knock back any large air bubbles and creates the "foot"-the puffy bit you see on the edge of the inside of each cookie. Leave the macarons on the counter for half an hour to allow the cookies to develop the skin which will produce a shiny finish once baked.
While the cookies are resting, preheat the oven to 350°F/325°F convection.
Once the cookies have rested for thirty minutes, put them in the oven and bake for 6 minutes. Then rotate the pans and cook for another 6-7 minutes until just barely starting to brown.
Remove the macarons from the oven and allow to cool for about five minutes on the pan, then transfer to a wire cooling rack or parchment paper laid out on the counter to finish cooling.
Once the macarons are fully cool, sandwich two cookies together with jelly or jam.