Preheat oven to 350° F. Line an 8-inch square pan with parchment paper. Alternatively, grease the pan.
In the mixing bowl of an electric mixer, press the lemon zest into the sugar with your fingertips. Add eggs and the egg white and whisk 5-10 minutes at high speed. The mixture will be pale yellow and somewhat thick. (Alternatively, you can whisk by hand, which is a workout but doable.)
In a small bowl, whisk together the almond flour, potato starch and salt. (If either the almond flour or the potato starch are clumpy, sift them into the bowl before whisking together.)
In a small bowl, whisk together the almond butter, olive oil, vanilla, and lemon juice until smooth. With the electric mixer, whisk this mixture into the egg/sugar mixture until fully incorporated. You may have to stop the mixer to wipe down the sides with a rubber spatula.
Add the dry ingredients, mixing just until fully incorporated.
Fold in blueberries and spread into prepared pan.
Bake 40-45 minutes. The edges should be golden brown, the top should be lightly browned, and a toothpick inserted in the middle should come out clean. Cool completely in pan on wire rack.