Preheat the oven to 375°F and line a 12-cup muffin pan with paper liners. In a medium bowl, combine the flour, baking powder, and salt by whisking thoroughly. In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl using a hand mixer, cream together the butter and granulated sugar on medium-high speed for about 5 minutes until pale and fluffy. Lower the speed to medium and incorporate the eggs one at a time, ensuring each is fully blended before adding the next. Mix in the vanilla extract. Adjust the speed to low, then add the dry ingredients in three parts, alternating with the milk, mixing just until a few streaks of flour remain visible. Gently fold in the diced strawberries with a rubber spatula. Divide the batter equally among the prepared muffin liners, filling nearly to the top. If desired, top with extra diced strawberries and a sprinkle of sugar. Bake for 18 to 20 minutes, or until golden on top and a toothpick inserted into the center emerges clean. Allow the muffins to cool briefly in the pan, then transfer them to a wire rack to cool completely. Store in an airtight container for up to 3 days or freeze for up to 1 month.