Preheat the oven to 375 degrees F, and grease or line a 12-cup muffin tin.
In a medium bowl, combine the cornmeal, flour, baking soda, salt, and optional lemon zest and flaked or shredded coconut. Place the lemon juice in a one-cup liquid measure and add the coconut milk to equal one cup. Set aside.
In a mixing bowl, whisk the eggs into the melted coconut oil. Stir in the sugar and the coconut milk-lemon juice mixture.
In two batches, add the dry ingredients to the wet ingredients, stirring just enough to thoroughly combine. Fold in the blueberries.
Transfer the batter to the prepared muffin tin. I like to use a large ice cream scoop with a release to make this easy and mess-free. Sprinkle the unbaked muffins with a little shredded coconut, if desired.
Bake for 17-20 minutes, depending on the oven, or until the muffins pass the toothpick test. Take care not to over-bake to avoid dry muffins. Remove from the oven, cool muffins in the pan for 5 minutes, and then remove to a rack to cool thoroughly. Store in an airtight container. The muffins will stay fresh on the counter of a couple of day. Storing in the fridge will prolong freshness but make the muffins firm. When stored this way, reheat gently in the microwave to warm and soften. Also, a quick fix for dry corn muffins–and this applies to any recipe–is to wrap them in a damp paper towel and gently warm in the microwave.
Melt butter in large skillet. Remove from heat and stir in sugar. Quickly add eggs and beat until well blended. Combine buttermilk with baking soda and stir into mixture in pan. Stir in cornmeal, flour, and salt until well blended and few lumps remain. Pour batter into the prepared pan.
Bake in the preheated oven for 30 to 40 minutes, or until a toothpick inserted in the center comes out clean.