A couple notes: I prefer to use flexible silicone mini muffin pans with no paper liners for this recipe, but you can also prepare metal mini muffin pans with paper liners. Also, I found that there are different sized mini muffin pans out there, so your yield and baking time may vary a bit. The silicone pans I used yield a little bigger mini cupcake than others, which I also happen to like.
Whisk flour, baking powder, and salt in medium bowl and set aside. In a large bowl, beat butter until smooth. Add sugar and beat to blend. Beat in eggs 1 at a time, then the lemon juice, lemon peel, and food coloring. Batter may look curdled, but that's just fine. Beat in the flour mixture alternately with the buttermilk, in 3 additions. Place about 1 tablespoon of batter into bottom of each cupcake hole. Place 1 fresh raspberry on top of the batter, in the center. Cover raspberry with more batter, about 3/4 full.
Bake cupcakes until tester inserted into center comes out clean. This took about 20 minutes for me, but it will depend on the size of your tins, so pay close attention to your baking time. Cool 10 minutes and remove from pan. Cool completely before adding frosting.
for the fresh raspberry buttercream:
Cook the raspberries in a medium saucepan over medium heat, stirring frequently until the raspberries are broken down into a sauce. Set a fine mesh strainer lined with 2 layers of cheese cloth and set over a bowl. Pour the raspberry sauce over the cheese cloth to remove the seeds. Gather up the ends of the cheese cloth and press out all the raspberry juice with the back of a spatula. You should be able to get at least a half cup of juice from this amount of berries, but I can usually press out almost 3/4 of a cup.
Pour the raspberry juice back in the pot. Simmer until the juice reduces to a 1/4 cup. It will be a very rich red and concentrated sauce. Set aside to cool completely.
With a mixer, cream the butter with a paddle attachment on medium high speed about 2 minutes, until lightened in color and a bit fluffy.
Add 2 cups of powdered sugar, the 1/4 cup of cooled raspberry sauce, lemon juice, vanilla, and salt. Mix until smooth. Add another 1-1/2 cups of powdered sugar and mix until smooth. If you want the frosting less stiff, add some milk, 1 tablespoon at a time. I did not add any milk to mine, and thought it was perfect for piping.
to assemble the lemon baby cakes with fresh raspberry buttercream:
Fit a pastry bag with a medium star tip (I used a Wilton #21) and pipe the frosting onto your baby cakes.
Nutrition information is automatically calculated by Spoonacular. I am not a nutritionist and cannot guarantee accuracy. If your health depends on nutrition information, please calculate again with your own favorite calculator.