If you want to use fresh raspberries, mash them and strain through a fine-mesh sieve to remove the seeds. I didn’t strain mine. You should get about 2-3 tablespoons of smooth purée. Set aside.

In a large bowl, beat the softened butter with an electric mixer on medium-high speed for about 2-3 minutes, until pale and fluffy.

Add 2 cups of powdered sugar and mix on low speed until combined, then increase to medium speed and beat until smooth.

Mix in the raspberry purée, lemon juice, lemon zest, vanilla extract, and salt.

Add the remaining powdered sugar ½ cup at a time until you reach your desired consistency. If the frosting is too thick, add a splash of lemon juice or heavy cream (1 tablespoon at a time).

Beat on medium-high speed for another 2-3 minutes until the buttercream is light, fluffy, and smooth.