Preheat oven to 425°F. Line 12 standard muffin cups with paper liners or spray with nonstick cooking spray.
In a large bowl, add the lemon zest, granulated sugar and brown sugar. Mix the ingredients together with your fingertips until the sugar is moistened and fragrant.
To the sugar mixture, add the flour, baking soda and salt. In another bowl, combine the egg, lemon juice, buttermilk and oil. Create a small well in the dry ingredients, pouring the wet ingredients into the well and stirring just to combine. Gently fold in the raspberries.
Divide batter evenly into the prepared muffin wells. The wells will be very full. Sprinkle the tops with coarse sugar.
Bake at 425°F for 10 minutes. Leaving the oven door closed, set the oven temperature to 350°F and continue to bake for another 7-9 minutes, until the tops are golden and a toothpick inserted into the center comes out clean.
Let muffins cool in the pan for about 5 minutes before removing them to a wire rack to finish cooling.
Notes
My favorite coarse sugar for topping muffins and quick breads is Sugar in the Raw Turbinado Cane Sugar.
If using frozen raspberries, do not thaw them before adding them to the batter.
If your berries are on the larger size, you can halve them before adding them to the batter to more evenly distribute them throughout the muffins.
Store muffins in an airtight container at room temperature for 1-2 days or in the refrigerator for up to 4 days.
Substitutions:
You may substitute the vegetable oil for any neutral-flavored oil, such as avocado oil.
For a dairy-free version, make a buttermilk substitute using dairy-free milk.
For a vegan version, substitute the buttermilk as noted above and swap the egg for a flax egg (1 tablespoon ground flax + 3 tablespoons water, allow to thicken for 5 minutes).