Preheat the oven to 350 degrees F. Spray 2 - 8” cake pans with cooking spray containing flour to prevent sticking. Set the pans aside.
In a large bowl, whisk together the milk, melted butter and eggs. Add in the dry muffin mix and stir to combine. If using blueberry mix as shown, drain the cans of blueberries and rinse them well with cold water. Use a spatula to gently fold in the berries until combined.
Divide the cake batter evenly between the two pans and place in the oven to bake for 35 minutes, or until a knife comes out mostly clean with moist crumbs attached. Remove and let cool in the pans for about 10 minutes before turning the cakes out onto a cooling rack.
To assemble the cake, once cooled, place the first layer in the center of a cake stand or plate. Scoop about ⅓ to ½ c of frosting and spread in an even layer. Place the top layer on top of that.
Spread the remaining frosting over the top and sides of the cake, scrape away most of the sides to create a minimally frosted cake. Take the remaining frosting and place in a piping bag and swirl frosting on top of the cake.
Notes
Tips
If you want a rounded top, put the first layer on the cake plate with the top facing down, frost middle, then the second layer should have the rounded top set on top of that.
If you want a flat top of the cake, set the first layer on the cake plate facing up with frosting on top of that with the top layer upside down so the top of the cake is flat.