Preheat the oven to 375°F/190°C/Gas Mark 5, no fan.
Wash the blueberries, pat them dry with paper towels, set aside.
Prepare a muffin pan (standard size) and line it with 12 paper liners. Spray the liners with a non-stick baking spray (optional).
Add the eggs, yogurt, butter, sugar, lemon zest, vanilla, baking powder, baking soda, and salt into a large bowl. Whisk until well combined.
Add the flour, fold in with a spatula until almost combined (you should still see some streaks of flour in the batter).
Add the blueberries (reserve some blueberries to put on top), fold in with a spatula until evenly distributed and there are no streaks of flour visible. Don't overmix the batter.
Divide the batter evenly between 12 muffin liners.
Put the reserved blueberries on top of the batter, press them in. Sprinkle with brown sugar.
Bake for about 25 minutes or until a wooden skewer/cake tester comes out clean.
Place on a cooling rack to cool slightly then enjoy!