Preheat the oven to 350°F (175°C).

In a bowl, combine all-purpose flour, granulated sugar, unsweetened cocoa powder, baking powder, baking soda, and salt.

In another bowl, whisk together egg, milk, vegetable oil, and vanilla extract.

Mix the wet ingredients into the dry ingredients until just combined.

Gently fold in fresh raspberries.

Pour the batter into a greased cake pan.

Bake in the oven for 25 minutes or until a toothpick comes out clean.

Let the cake cool before frosting.

For the frosting, beat together softened butter, powdered sugar, cocoa powder, vanilla extract, and milk until smooth.

Frost the cooled cake and serve.