Preheat oven to 425°F (220°C). Prepare muffin tin with grease or liners.
In a bowl, whisk together flour, salt, cinnamon, baking powder, and baking soda.
In a separate large bowl, mix melted butter, sugar, vanilla, and sourdough discard.
Add eggs one at a time, mixing well after each.
Gradually add dry ingredients to wet, mix until just combined.
Fold in blueberries gently.
Optional: Chill the batter for 1 hour for enhanced flavor.
Fill muffin cups with batter.
Bake at 425°F for 5-6 minutes, then reduce heat to 350°F and bake for 13-15 minutes more.
Test for doneness with a toothpick and cool before serving.