Preheat oven to 425 degrees Fahrenheit. Grease a muffin pan with nonstick spray.
Whisk together flour, baking powder, and salt. In a large bowl, cream together butter and 1 1/4 cups sugar until light and fluffy, scraping down the sides of the bowl often. Add eggs one at a time, beating well after each addition.
Add half the flour mixture and beat until just blended. Beat in buttermilk, then add remaining flour mixture and beat until blended. Gently fold the blueberries into the batter.
Spoon batter into prepared muffin pan. Sprinkle with 1 tablespoon sugar. Place pan in oven and immediately reduce heat to 375 degrees Fahrenheit.
Bake for 30 minutes or until muffins are golden brown.
Cool in pan for 5 minutes. Move to wire rack to cool completely.