Yield: 12 cookies
Directions
Preheat oven to 350°F. Line a large baking sheet with parchment paper.
On a medium baking sheet scatter hazelnuts. Roast until fragrant and the skins are blistered, 12-15 minutes. Let cool slightly, then transfer 1⁄2 cup hazelnuts to a food processor along with the flour. Pulse until hazelnuts are ground into a fine flour. Roughly chop remaining hazelnuts and set aside.
Transfer hazelnut-flour mixture to a large bowl along with oats, cinnamon, baking soda, and salt. Stir to combine.
In a large bowl mash bananas. Stir in egg, honey or maple syrup, oil, vanilla, and lemon zest until smooth. Stir in oat mixture until thoroughly combined. Fold in chopped hazelnuts and blueberries.
Pack cookie mixture into a 1⁄3-cup measure, then tap the measuring cup onto the baking sheet so the cookies fall out in rounds. Flatten each cookie slightly.
Bake until browned and set, 15-18 minutes. Let cool completely on baking sheet.