Preheat the oven to 425°F (220°C). Prepare the baking tin by lining or greasing it.
In a mixing bowl, combine sugar and lemon zest. Rub the sugar with lemon zest until well combined.
Add eggs and whisk for 2-3 minutes or until pale in color. Whisk in melted butter until well combined.
Add milk mixture, vanilla bean paste, sour cream, and oil. Mix until well combined.
In a separate bowl, combine dry ingredients: flour, baking powder, baking soda, and salt. Reserve 2 tablespoons of dry mixture to coat mixed berries.
Pour wet mixture into dry ingredients and mix until just combined. Toss mixed berries in reserved dry mixture and add to batter. Do not overmix.
Let the batter sit at room temperature for 30 minutes. Divide batter evenly among muffin cups. Add more berries on top if desired.
Bake for 5 minutes, then reduce oven temperature to 375°F (190°C). Continue baking for 15 minutes or until a toothpick inserted in the center comes out clean.
Allow muffins to cool in tin for 5 minutes before transferring to a wire rack to cool
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