Place the ingredients in a small sauce pan on medium low heat.
Mash the berries with the back of a spoon or muddler and stir occasionally.
You want to reduce the amount of liquid, intensify the flavor, and thicken the liquid so aim to cook until the mixture is reduced at least by half.
Strain the reduction and set aside to cool.
For the Cake
Preheat oven to 350 °F, butter four 6' pans or two 9″ cake pans and cut parchment paper rounds for the bottoms.
Sift the dry ingredients
Add flours, Baking powder, cream of tartar, and salt in bowl.
In bowl of electric mixer beat butter on high until butter is lighter and creamed, about 3-5 minutes.
Lower speed of mixer to low and add eggs and extracts until mixed, and then slowly add confectioner sugar until blended.
Alternating between, flour mix, sour cream and milk add in thirds (1/3 flour, ⅓ sour cream, ⅓ milk) until, blended.
Stir in the coconut.
Place about a cup for the batter in a separate bowl and mix in about 1/4 of the blackberry reduction. If the mixture seems too wet you can fold in some more almond flour.
Divide mixture between the prepared pans. Swirl in the blackberry infused batter.
Bake at 350F until centers are set. About 30 minutes.
For the Buttercream
Cream the butter until it lightens and changes texture, at least 5 minutes. Beat in the cup of confectioners' sugar. Add the mascarpone cheese and 1/4 cup of the reduced poaching liquid. beat JUST until combined. If you over beat the texture will loose it's silkiness.
Divide the batch in two and beat in about 1/4 cup of the blackberry reduction
To Assemble
Add blackberry buttercream to between each layer. Cover in plain buttercream and smooth sides. (I made mine a naked cake by scraping more from the edge)
Top cake with blackberries.
Video
Notes
If you’re not using 6-inch pans, double the recipe for 8-inch pans or triple the recipe for 9-inch pans.
You can substitute whole milk yogurt for the sour cream if desired, I do it all the time and can’t really tell the difference.
To get FLAT layers that are moist inside and out try using cake strips! You can buy a set online or make your own from foil and paper towels at home. I made a wholeblog post on it so check it out if you’re interested!
WHAT IF YOU CAN’T FIND MASCARPONE ANYWHERE?!?A while back I was making a cake with a mascarpone buttercream and realized mine had expired! I didn’t have time to go to the market so I followed Nigella’s advice for a reasonable facsimile and mixed the following ingredients together until combined. Make sure they are all at room temperature!8oz cream cheese1/4 cup heavy cream2 tbs unsalted butter