01 - Preheat the oven to 350°F. Line a 12-cup muffin tin with paper liners or lightly grease each cup.
02 - In a large bowl, whisk together almond flour, coconut flour, baking powder, baking soda, and salt until well combined.
03 - In a separate bowl, whisk the Greek yogurt, eggs, honey or maple syrup, melted coconut oil or butter, and vanilla extract until smooth.
04 - Add the wet ingredients to the dry ingredients. Stir gently with a spatula until just combined—do not overmix.
05 - Fold in the blueberries and lemon zest if using, distributing evenly throughout the batter.
06 - Divide the batter evenly among the prepared muffin cups. Cups will be quite full.
07 - Bake for 22-26 minutes, or until the tops are golden 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.