• Preheat the oven to 350°F(180°C). Line a 12-hole muffin pan with paper cases. Slightly oil paper case with oil spray, Set aside.
• In a large bowl combine flour, baking powder, salt, and sugar. Set aside.
• In another bowl, whisk egg, milk, lemon juice, vanilla, melted butter, and lemon zest.
• Pour the wet ingredients into the dry ingredients.
• Fold in berries halfway through and stir until just combined. Don't over-stir or the muffins will be dense. The batter should be thick, and that's normal.
• Add 3 tablespoons to each muffin paper case.
• Bake the muffins in the center rack of the oven for 25 minutes to 35 minutes baking time can vary. It takes longer if you added frozen berries to the batter.
• The muffins are ready when golden brown and a pick inserted in the center of the muffins comes out clean.
• Cool down on a wire rack for 1 hour before eating.

Storage

• Store in a sealed container for up to 2 days at room temperature, 4 days in the fridge, or 3 months in the freezer. Thaw at room temperature the day before.