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 oil.
02 - In a large bowl, whisk together almond flour, coconut flour, baking powder, baking soda, and salt until thoroughly blended 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 emulsified.
04 - Pour the wet ingredients into the dry ingredients. Using a spatula, fold gently until just combined—do not overmix or the muffins will become dense. The batter will be thick.
05 - Gently fold in the blueberries and lemon zest, being careful not to crush the berries. If using frozen berries, add them directly from the freezer.
06 - Divide the batter evenly among the 12 prepared muffin cups, filling each cup to the top. The batter will be quite full, which is normal.
07 - Bake for 22 to 26 minutes, or until the tops are golden brown and a toothpick inserted into the center of a muffin comes out clean or with just a few moist crumbs.
08 - Let the muffins cool in the tin for 5 minutes, then carefully transfer to a wire rack to cool completely before serving.