Preheat the oven to 400 degrees. Line a muffin tin with paper baking cups. Melt the butter. Whisk it in a large bowl with the egg and 6 tablespoons of sugar. Add the salt, baking powder, milk, flour and blueberries, and fold gently until all the ingredients are mixed. Spoon the batter into 12 baking cups. Combine the remaining 1 tablespoon of sugar with the cinnamon and sprinkle about 1/4 teaspon onto each muffin ( you will have a little left over). Bake in the middle of the oven until the muffins are brown and lightly firm, about 1/2 hour. Cool the muffins in the pans for 5 minutes. Then spread out a clean kitchen towel, turn the pans on their sides, and tap the muffins out onto the towel. Let the muffins finish cooling on a wire rack. Makes 12 muffins.