Preheat the oven to 350°F (175°C). Line a muffin tin with cupcake liners

In a large bowl, whisk together the flour, sugar, cocoa powder, baking soda, and salt

Add the water, vegetable oil, vinegar, and vanilla extract to the dry ingredients and mix until just combined

Gently fold in the mashed raspberries

Divide the batter evenly among the cupcake liners, filling each about two-thirds full

Bake for 18-20 minutes, or until a toothpick inserted into the center of a cupcake comes out clean

Allow the cupcakes to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely

For the frosting, beat the butter until creamy. Gradually add the powdered sugar, beating until light and fluffy

Add the raspberry puree and vanilla extract, mixing until well combined

Frost the cooled cupcakes with the raspberry frosting and garnish with fresh raspberries