In a large bowl, whisk together baking blend, cornstarch, baking soda, and sea salt. In a medium bowl, whisk together eggs, buttermilk, coconut oil, vanilla, lemon zest, lemon juice, and honey. Gently fold wet ingredients into flour mixture until just combined, and some small lumps remain. Do NOT over-mix. Gently fold in blueberries. Let batter stand for 10 minutes.