Whisk together the flour, salt, baking powder, baking soda, and sugar in a medium bowl; set the dry mix aside.

In a separate bowl, whisk the eggs, buttermilk, and vanilla extract (if using) until the mixture is light and slightly foamy. Whisk in the melted butter.

Add the dry ingredients to the wet ingredients and stir just until combined. Do not overmix — a few small lumps are fine.

Preheat a large frying pan over medium-low to medium heat. Lightly grease the pan with a little butter. Test the heat: a drop of water should skitter and evaporate immediately.

Using a 1/4-cup measure, pour batter onto the hot, greased pan for each pancake. Immediately sprinkle 1–2 tablespoons of blueberries on top of each pancake.

Cook the pancakes until bubbles form on the surface and the edges start to set, about 2–3 minutes. Flip and cook the other side until golden brown, about 2 minutes more.

Transfer cooked pancakes to a baking sheet fitted with a cooling rack and keep warm in a 200°F oven, or serve immediately.

Serve the pancakes with additional blueberries and butter if desired.