Preheat oven to 325 degrees.

Line three, 8″ round pans with parchment paper. Grease and flour the sides.

In a stand mixer fitted with paddle attachment, mix together water, sour cream, oil, extracts and egg whites.

In a separate bowl, stir together cake mix, flour, sugar, and salt.

Turn mixer on low. Gradually pour in cake mix/flour mixture.

Mix on low for 4 minutes. Some lumps should remain.

Pour batter into prepared cake pans. Bake 18-20 minutes, or until toothpick inserted into center of cake comes out clean.

Cool cakes in pans for 4 minutes then remove to racks to finish cooling. Let cool completely before frosting.

Thaw raspberries and strain juice from berries. For this step I put a large strainer over a bowl and let the berries thaw in the strainer.

Add enough water to the juice in the bowl so that you have 3/4 cup of liquid.

Combine juice mixture with sugar, lemon juice, and cornstarch in a small saucepan. Cook over medium heat, whisking constantly, until mixture thickens. Once mixture thickens, remove from heat and set aside.

Place the raspberries in a mesh strainer. Place strainer over bowl and press berries with spoon so that pulp falls into a bowl. Strain until you have 1/2 cup of pulp.

Once the mixture in the saucepan has cooled, add the raspberry pulp and raspberry liqueur. Stir well. Transfer to airtight contained and place in refrigerate for at least 3 hours before using.

Place butter and shortening in bowl of stand mixer fitted with paddle attachment. Beat on medium high speed until mixture is smooth and has lightened in color.

Add powdered sugar 1/2 cup at a time. Start on low to mix sugar in, then beat on high speed until well incorporated. I find it best to place a shield over the mixer when working with powdered sugar.

Add vanilla and sea salt. Mix until well combined.

Add milk or heavy cream, 1 tablespoon at a time, until desired consistency is achieved.

Thaw raspberries and strain juice from berries. For this step I put a large strainer over a bowl and let the berries thaw in the strainer. Use a spoon to press berries into strainer so that pulp falls into bowl.

Place butter and shortening in bowl of stand mixer fitted with paddle attachment. Beat on medium high speed until mixture is smooth and has lightened in color.

Add powdered sugar 1/2 cup at a time, followed by 1 tbsp of raspberry pulp. Mix well after each addition.

Mix in pinch of sea salt.

Level cakes.

Pipe a border of vanilla vanilla buttercream over the leveled top of two of the layers. Divide the raspberry filling between the two layers and spread to piped border.

Frost over raspberry filling with vanilla buttercream (I find it easiest to pipe a thin circular layer and spread with an offset spatula).

Stack two layers with filling. For top layer, place top down.

Frost outside of cake with vanilla buttercream. I like to first do a light, crumb layer, let the cake sit in the fridge for about 20 minutes, and then finish.

Decorate with raspberry buttercream.