Position a rack in the center of the oven. Preheat the oven to 350°F (180°C) and line a cupcake tin with cupcake liners.
In a mixing bowl whisk together the cake flour, baking powder, and salt. Set aside. 1 ¼ cups (150 g) cake flour 1 ¼ teaspoons baking powder ¼ teaspoon salt
In the bowl of a stand mixer fitted with a paddle attachment, beat together the butter and sugar until well combined on medium speed until light and fluffy, about 2 to 3 minutes scraping the sides of the bowl if needed. 8 tablespoons (1 stick, 113 g) unsalted butter, ¾ cup (150 g) granulated sugar
Add the eggs one at a time, beating to combine. Scrape down the bowl as needed. Add the vanilla and mix until well combined. 2 large eggs 1 tablespoon vanilla extract
Pour half the buttermilk and half the dry ingredients in and mix until almost combined. Add the remaining buttermilk and dry ingredients and mix until a few flour streaks remain. Don’t overmix. ½ cup (120 ml) buttermilk
Add the diced strawberries and fold them in gently by hand with a spatula or wooden spoon until just combined. 1 ½ cups (200 g) diced strawberries
Fill each cupcake about 2/3 full of batter and bake for 18-20 minutes or until a toothpick inserted comes out with a few moist crumbs.
Let the cupcakes cool in the cupcake tin on a wire cooling rack for 3-5 minutes before removing to cool on the wire rack outside the tin. Let cool completely before frosting.