Preheat oven to 350°F. Grease the sides and bottom of a 7 inch round springform pan. Line the bottom of the pan with parchment paper.

Beat eggs on highest speed with a stand mixer using the whisk attachment, until triple in volume, about 8 minutes. The egg batter should turn a very pale yellow and become quite thick. Add in sweetener and beat for another 2 minutes on highest speed. The mixture should be even fluffier and even whiter in color. The eggs should now be quadrupled in volume. If you lift the whisk, the batter that runs off should hold its form on top of the egg batter for a few seconds before sinking back in.

Add peanut butter into a large mixing bowl. Add in ⅓ of the egg mixture. Gently fold with a spatula in the same direction until all of the egg is mixed in and no egg streaks remain. Do not use a whisk or mixer, otherwise you will deflate the eggs too much. Then add another ⅓ of egg mixture and fold again until no egg streaks remain. Repeat with final ⅓ of egg mixture. It is okay if you have tiny flecks of peanut butter remaining in your batter (see photo above). If you try to have a uniform batter with no flecks of peanut butter, you will deflate the eggs too much.

Pour batter into springform pan. Bake for 30-35 minutes (mine took 32 minutes) until knife inserted in the middle comes out clean. Let cake cool before cutting and serving. The top of the cake will initially be very puffy and round but it will deflate slightly and level off as it cools. Top with Swerve confectioners before serving. Store uneaten cake in an airtight container to keep cake from getting dry.