Preheat the oven to 425°, then line a 12-cup muffin pan with paper muffin liners. Set aside.
Cream sugar and butter together in a large mixing bowl. Add each large egg and mix until combined.
In a separate large bowl, combine gluten-free flour, salt, baking powder, and baking soda.
Alternate adding the buttermilk and dry ingredients to the butter mixture.
Once everything is combined, add the fresh berries. Fold them into the muffin batter with a wooden spoon or a silicone or rubber spatula (I prefer this one!)
Scoop ¼ cup muffin batter into each muffin liner. Sprinkle with coarse sugar.
Bake in the oven for 6 minutes and then turn the temperature down to 375° and bake for 18 more minutes.