01 - Preheat the oven to 350°F. Line a 12-cup muffin tin with paper liners or lightly grease each cup with cooking spray or butter.
02 - In a large mixing bowl, whisk together almond flour, coconut flour, baking powder, baking soda, and sea salt until thoroughly combined and no lumps remain.
03 - In a separate medium bowl, whisk the Greek yogurt, eggs, honey or maple syrup, melted coconut oil or butter, and vanilla extract until smooth and fully incorporated.
04 - Pour the wet ingredients into the dry ingredients. Using a spatula, fold gently until just combined. The batter will be thick—do not overmix as this can result in dense muffins.
05 - Gently fold in the blueberries and lemon zest, taking care not to crush the berries. If using frozen blueberries, add them directly from the freezer.
06 - Divide the batter evenly among the 12 prepared muffin cups, filling each cup nearly to the top. The batter will be substantial, so use an ice cream scoop for even distribution.
07 - Bake for 22 to 26 minutes, or until muffin tops are golden brown and a toothpick inserted into the center comes out clean or with just a few moist crumbs.
08 - Allow muffins to cool in the tin for 5 minutes before transferring to a wire rack. Cool completely before serving or storing.