Preheat the oven to 375 degrees. Line muffin tins with paper liners.
Sift the flour, baking powder, baking soda, salt, and cinnamon together in a large bowl. Stir with your hand to be sure the ingredients are combined. In another bowl, combine the milk, eggs, and melted butter. Make a well in the middle of the dry mixture, pour the wet mixture into the well, and stir until just combined. There will be some lumps but don’t overmix the batter! Add the blueberries, raspberries, strawberries, and sugar and stir gently to combine.
Using a 2¼-inch ice cream scoop, spoon the batter into the muffin cups to fill the liners. Bake for 20 to 25 minutes, until a cake tester comes out clean and the tops are nicely browned.
Copyright 2006, Barefoot Contessa at Home by Ina Garten, Clarkson Potter/Publishers, All Rights Reserved