Preheat oven to 350F. Grease and flour three 6" cake rounds, line with parchment.
In a medium bowl, whisk flour, baking powder, salt, and cocoa powder. Set aside.
Using a stand mixer fitted with the paddle attachment, beat butter until smooth. Add sugar and beat on med-high until pale and fluffy (2-3mins).
Reduce speed and add eggs one at a time, fully incorporating after each addition. Add vanilla, red color gel, and vinegar.
Alternate adding flour mixture and buttermilk, starting and ending with flour (3 additions of flour and 2 of milk). Fully incorporating after each addition. Do not overmix.
Spread batter evenly into prepared pans. Smooth the top with a spatula.
Bake for approx. 30mins or until a toothpick inserted into the center comes out mostly clean.
Place cakes on wire rack to cool for 10mins then turn out onto wire rack to cool completely.
Buttercream:
Prepare a stand mixer with a whisk attachment. Whisk butter until creamy. Reduce speed to low and add in icing sugar 1 cup at a time until well blended. Increase speed to med and beat for 3 minutes.
Add vanilla and 1 Tbsp cream and continue to beat on medium for 1 minute.
- Reserve 1.5 cups of the white frosting to frost the inside layers and crumb coat the cake.
- Reserve 1/4 cup of the white frosting to color red.
- Reserve 1/4 cup of the white frosting to color green.
For the remaining frosting, add enough color get to get it to the desired shade(s) of dark grey. I ended up using the entire bottle to get 3 different shades. Once it got to a dark enough grey shade, I removed 1/4 of the buttercream, then I added more black and did the same one more time. With the remaining buttercream I added the rest of the color gel for the darkest shade.*
See tutorial pictures above for decorating technique.
Notes
*Note: all of the colors will darken over time. So much so that you can't really tell that I have 3 different shades of grey. You may want to save some time and just do one dark shade. Inspired by this House Targaryen Cake.