Additional fresh raspberries or flowers for decorationoptional
Instructions
First, preheat oven to 350° Fahrenheit, and grease three 9-inch round cake pans with butter or cooking spray. Then, grind the pistachios. I blitz the raw, unsalted pistachios in a nutribullet or food processor until they're finely ground (an electric coffee grinder or a Vitamix also works - anything that gets a finely-ground flour out of the nuts). Blitz them up 1/2 cup at a time or they may turn into pistachio butter. Pack down the pistachio flour when you measure. Then, whisk the resulting pistachio flour with the gluten free 1-1 flour, baking powder, salt, and baking soda in a medium bowl, then set aside.
Then, in a large bowl, whisk together the eggs, canola oil, vanilla, rose water, sour cream, milk, and sugar, until smooth. Dump in the dry ingredients and stir everything together until combined. Then pour the batter evenly into the three greased pans. Bake for 30-35 minutes or until tops spring back when touched and a skewer inserted into the center of each cake comes out clean. Let cakes cool completely before frosting. I recommend letting cakes cool, then turning cakes out, wrapping them in plastic wrap, returning them to the pans, and freezing them for 2 hours so that construction is easier.
While cakes are cooling, make the buttercream, whipped cream, and mashed raspberries! Buttercream first. In a large bowl, using an electric mixer, beat together the room temp butter and add in 1 cup of the powdered sugar at a time. Then add in the rose water and lemon juice and beat until smooth. Then, blitz up the freeze dried raspberries in a food processor or nutribullet until they're a fine powder. Sift the powder (to remove seeds) into the frosting (I usually use three packages/bags of freeze dried raspberries). Beat in the powder and the salt until smooth, tasting as you add ingredients to get your desired tartness/sweetness combo. Add more powdered sugar if the frosting is too loose, and add more lemon juice to bring out more of the tartness of the raspberries.
Next, make the whipped cream and mashed raspberries. Mash about a cup of raspberries in a small bowl with a fork or spoon until it looks like jam. Then, in a large bowl, beat the heavy cream using a whisk or an electric mixer until soft peaks form. Add the powdered sugar and 1/3 cup of the mashed raspberries into the cream. Continue to beat until stiff peaks form. Save the remaining mashed raspberries to go on top of the cake.
Then construct the cake! If you froze your cake layers, unwrap them now. Place one layer on a serving tray/plate/cake stand. Frost the top of this layer with a thin layer of buttercream, spreading evenly. Then scoop a couple of cups of buttercream into a piping bag and cut a 1/2 inch opening. Pipe a ring of buttercream on the edge of the layer and fill the space in the center with 1/2 of the whipped cream. Add the second cake layer on top, and repeat the filling steps. Finally, add the final layer and frost with buttercream. Crumb coat the entire cake with buttercream, then place in the fridge or freezer fr 20-30 minutes to firm up, then remove and apply the final coat of frosting. Spread the top of the cake with the remaining mashed raspberries, then scoop the remaining buttercream into a piping bag and decorate the cake how you like.
The cake will keep for about a week in the fridge, or you can continue to freeze the finished cake for a few hours and remove from freezer a few hours before serving.