Preheat your oven to 375°F (190°C). This ensures the muffins bake evenly and rise properly.
In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, and salt until well combined. This helps to distribute the leavening agents evenly throughout the flour.
In another bowl, mix the buttermilk, melted butter, eggs, and vanilla extract until smooth. The buttermilk adds moisture and a slight tang, while the butter provides richness.
Pour the wet ingredients into the dry ingredients. Gently fold together using a rubber spatula until just combined. Be careful not to overmix, as this can lead to dense muffins.
Gently fold in the blackberries, taking care not to crush them. This will ensure that the muffins have beautiful pockets of fruit.
Bake the Muffins
Line a muffin tin with paper liners or grease it lightly with cooking spray. This prevents the muffins from sticking.
Spoon the batter into the prepared muffin tin, filling each cup about 2/3 full. This allows room for the muffins to rise without overflowing.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean. This indicates that the muffins are fully baked.
Remove the muffins from the oven and let them cool in the tin for 5 minutes before transferring them to a cooling rack. This helps them set and makes them easier to remove.
Notes
These muffins can be stored in an airtight container at room temperature for up to 3 days or frozen for up to 3 months. To reheat, simply microwave for 15-20 seconds.