Preheat your oven to 375°F and line a muffin pan with liners.
In a large bowl, whisk the flour, baking powder, baking soda, and salt together until fully combined. These will be your dry ingredients-- set this aside for now.
Prep the wet ingredients. In a separate bowl, use your fingers to rub the sugar and lemon zest together until the sugar takes on a light yellow tint. Then, pour in the cooled butter, eggs, and vanilla. Whisk until very smooth and creamy.
Then, whisk in the milk, yogurt, lemon juice, and poppyseeds until smooth.
Create a well in the middle of your bowl of dry ingredients and pour in all the dry ingredients. Whisk until the batter comes together. Make sure to not overmix--lumps are okay.
Toss the blueberries with one tsp of flour to evenly coat them. Then, fold the blueberries into your muffin batter.
Divide the muffin batter evenly between the muffin cups. Sprinkle with demera sugar if desired. Bake for 18-21 minutes, or until muffins are set and a toothpick comes out clean.
After baking, let the muffins rest for 10-15 minutes in the pan before removing them. Enjoy!