01 - Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners or grease each cup lightly.
02 - In a large bowl, whisk together almond flour, coconut flour, baking powder, baking soda, and salt until thoroughly blended.
03 - In a separate bowl, whisk Greek yogurt, eggs, honey or maple syrup, melted coconut oil or butter, and vanilla extract until smooth and uniform.
04 - Pour wet ingredients into dry ingredients. Fold gently with a spatula until just combined, being careful not to overmix the batter.
05 - Fold in blueberries and lemon zest if using, distributing evenly throughout the batter.
06 - Divide batter evenly among the prepared muffin cups, filling each cup quite full.
07 - Bake for 22 to 26 minutes until tops are golden brown and a toothpick inserted into the center comes out clean.
08 - Let muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely before serving.