Preheat oven to 350 degrees Fahrenheit. Prepare three cookies sheets by lining them with parchment paper.
Pour the chilled aquafaba and the cream of tartar in a large electric mixer with the whisking beater. Turn on high and beat until soft peaks begin to form. It should take approximately 2-3 minutes.
Add the confectioner’s sugar, agave, and salt, and beat again, until the soft white peaks glisten. This step should take approximately 2-3 minutes.
Add the almond flour and beat until mixture is light and fluffy, with soft peaks remaining.
With a large piping tip on a pastry bag, open the lip of the bag wide, folding the top 1/3 over to the outside. Fill the pastry bag with the batter. The batter will be sticky, so to facilitate this step, put the bag inside a tall vase that you can fold the top 1/3 of the bag over the edge to steady the bag. Once filled, fold the top over.
Guiding the pastry bag, pipe 1-1/2-inch rounds about 1-1/2 inches apart. Top each cookie with pignoli nuts.
Refrigerate pan of cookies for 15-20 minutes before placing in oven. This step is critical as it will help reduce the spreading in the oven.
Bake cookies for 13-16 minutes, until just golden brown around the edges.
Remove from oven and slide cookies still on the parchment paper onto wire racks to cool.
Allow to cool completely, then peel cookies off the parchment paper and place onto a wire rack to continue setting.