Preheat your oven to 400° Fahrenheit while youprepare the muffin batter.o make the topping
In a bowl whisk together the flour, sugar, baking soda, baking powder, and salt and set aside.
Use a wooden spoon to mix in the melted butter
Mix in one lightly beaten egg until combined.
Fold in the yogurt and vanilla extract to the batter, the batter should remain thick.
With a rubber spatula or wooden spoon gently fold in the blackberries.
Divide the batter evenly between six muffin tin wells.
In a small bowl, mix 1 tablespoon of sugar and 1 teaspoon of lemon zest. Sprinke the tops with the sugar and lemon zest topping. Bake in a 400° preheated oven at for 18-20 minutes. Check for doneness and insert a toothpick into the middle of the muffin, if it comes out clean the muffins are done.
Cool 10 minutes before removing from muffin tin.
Notes
Don't overmix the batter, overmixing will cause a tough muffin.
Use a cookie scoop to get the batter into the muffin wells.
If you don't have a muffin pan then triple up on paper liners and cook on a small baking sheet.
Always preheat your oven, an oven thermometer is good to make sure your oven temperature is accurate.