Vanilla Cupcakes with Fresh Raspberries

To make the cupcakes:
2 Preheat oven to 350 (175C) degrees, with the oven racks arranged in the center. Place liners in a 12-cup muffin pan, or spray with non-stick spray and lightly dust with flour.
3 Mix the flour, sugar, baking powder and salt in an electric mixer on low speed with the paddle attachment.
4 Add the cubes of butter and increase the speed to medium. Mix until the mixture resembles coarse sand.
5 Add the egg whites, whole egg, buttermilk and extracts. Continue mixing until the batter is smooth and creamy, about 1 minute, stopping to scrape the sides of the bowl once or twice.
6 Portion the batter evenly into the muffins cups so that they are 2/3 full (approximately 3 tablespoon batter per cup)
7 Bake 20-25 minutes, until the tops spring back when lightly pressed.
8 Transfer the pan to a wire rack and cool 10 minutes. Remove the cupcakes from the pan and cool completely.
9 Use a pastry tip or a small paring knife to cut a small hole in the center of each cupcake (save the interior pieces to snack on). Spoon about a heaping teaspoon of the filling into each cupcake (leave any accumulated juices in the bowl), smoothing the tops. Spread about 2 tablespoons frosting on top of each cupcake.
To make the filling:
12 Lightly crush the raspberries in a small bowl with sugar. I prefer them less sweet, so 1 teaspoon is the right amount for my taste. Add more or less sugar as you like.
To make the frosting:
15 Beat the butter with the paddle attachment in a stand mixer until fluffy.
16 Add the sugar and salt and beat until smooth and incorporated. Add 1 tablespoon of the buttermilk and beat 1 more minute. Add the remaining tablespoon if it doesn't look smooth and spreadable.
17 Refrigerate until ready to frost the cupcakes.