Preheat oven to 400 degrees.
In medium sized bowl, combine yellow self-rising cornmeal mix, self-rising flour (sifted, spooned and leveled), and sugar.
Add beaten egg, buttermilk, vanilla extract, and lemon zest (if using). Stir until well combined. Batter should be smooth and pourable. If batter is thick and sticks to mixing spoon, add two more tablespoons of buttermilk. Stir until well combined. Set aside.
Sort fresh blueberries. Discard bad pieces. Rinse and pat dry. If using frozen blueberries, rinse under cold water. Pat dry.
Pour prepared blueberries into a medium sized bowl. Sprinkle with one tablespoon of flour. Toss until evenly coated. Set aside.
PREPARE MUFFIN TIN (LINERS): Arrange liners in muffin tin (optional). Do NOT preheat in oven. Baked muffins will have soft edges.
PREPARE MUFFIN TIN (GREASED): Grease muffin tin with vegetable oil or use vegetable oil spray. Preheat in oven for 7 minutes before filling with batter. Baked muffins will be golden brown with crusty edges.
Pour flour-coated blueberries into cornbread batter. Gently stir until well combined. Fill each muffin cup.
Bake 20 to 25 minutes OR until muffins are golden brown and toothpick inserted into center comes out clean.
After removing muffin tin from oven, carefully remove HOT. Arrange on a platter.
Serve warm or hot.