Preheat the oven to 350 degrees Fahrenheit. Line your cupcake tin(s) with liners, set aside.
In the bowl of a stand mixer, combine the 4 tablespoons softened butter and .75 cups of sugar. Cream on high for 2 - 3 minutes until smooth.
Add in 1 egg, .25 cup milk, 1 teaspoon vanilla and 1 tablespoon of lemon zest. Mix on medium speed until well combined.
Add in .75 cups flour, .75 teaspoons baking powder and .5 teaspoons of salt. Mix on low, scraping down sides, until well combined.
In a separate bowl, combined 1 cup frozen, chopped raspberries with 1 tablespoon of flour. Toss to coat the raspberries.
Fold the coated raspberries into the batter.
Fill the cupcake liners ½ full with batter and bake for 20 - 25 minutes at 350 degrees Fahrenheit.
While baking - start the frosting.
Raspberry Buttercream Frosting
In a pan, add 1 cup of raspberries and heat on low for 10 minutes.
Stir frequently until raspberries evaporate and then become a paste. Set aside to cool
In a mixing bowl, combine .75 cups softened butter, 2.5 cups powdered sugar, .5 teaspoons of salt and 2 tablespoons of milk.
Mix on low until well combined. Then, mix on medium high speed for another minute until it turns fluffy.
Add in the cooled raspberry paste and fold it all together.
Transfer the frosting to the piping bag and fit it with a large star tip.
Once cupcakes are cooled, pipe a large mound of frosting on each cupcake, creating a spiral shape.
Add a raspberry on top of each, if desired.
Notes
Tips
Don't over bake - Remove cupcakes from oven when the edges are golden brown and the centers are just set. They will bake a little more while cooling.
Use frozen raspberries - For the cupcake batter use frozen raspberries only. Otherwise they will add a lot of liquid to the batter, make it pink and sink to the bottom.
Correct frosting - you want your frosting to be light, fluffy and a little stiff. It should not drip off a spoon, but you still want it to be able to pipe onto the cupcakes. If it's too runny add more powdered sugar. If it's too stiff, add a little more milk.
Completely cool - allow cupcakes to cool completely before adding any frosting.
Storage
Keep in fridge for 3 - 5 days in an airtight container.
Keep in freezer for 3 months in an airtight container.