In a large bowl, whisk together the flour, cornstarch, sugar, baking powder, and salt until evenly combined.
In a separate bowl, whisk the Greek yogurt, whole milk, eggs, and vanilla extract until smooth; if the batter seems very thick, add 1–3 tablespoons extra milk to reach a slightly thick but pourable consistency.
If desired, stir in either 1 teaspoon grated lemon zest or 1/2 teaspoon cinnamon (do not use both).
Add the wet ingredients to the dry ingredients and stir gently just until combined; small lumps are fine—do not overmix.
Heat a large skillet or griddle over low to medium-low heat and melt about 1 tablespoon of unsalted butter until it bubbles.
Pour batter onto the skillet to form 3–4 pancakes at a time, leaving space between them. Cook 2–3 minutes until bubbles form on top and the undersides are lightly browned.
Flip the pancakes and cook 1–2 minutes more until golden and cooked through. Wipe out the pan with a paper towel, add more butter, and repeat with remaining batter.
Serve warm with maple syrup or blueberry syrup if desired.