1. Prepare Oven and Pans:

• Preheat your oven to 350°F (175°C).
• Grease and flour two 8-inch or 9-inch round cake pans thoroughly. For extra insurance against sticking, line the bottoms with circles of parchment paper, then grease and flour the parchment as well. Set aside.

2. Sift and Combine Dry Ingredients:

• In a large mixing bowl, sift together the all-purpose flour, unsweetened cocoa powder, baking powder, baking soda, and salt.
• Whisk these dry ingredients together until they are well combined.

3. Mix Initial Wet Ingredients:

• In another large bowl (or the bowl of your stand mixer), beat the granulated sugar and vegetable oil together with an electric mixer on medium speed until smooth and well combined. (Note: Oil and sugar won’t get “light and fluffy” like butter and sugar, just well mixed).
• Add the room temperature eggs one at a time, beating well after each addition until incorporated.
• Stir in the vanilla extract.

4. Add Food Coloring:

• Add the royal blue gel food coloring (start with 1 tsp, add more up to 2 tsp for desired intensity) to the wet mixture. If using, add 1-2 drops of violet gel food coloring – this helps achieve a deeper, truer blue and counteracts any greenish tones from the cocoa. Mix until the color is evenly distributed.

5. Prepare Buttermilk Mixture and Combine Batter:

• In a separate small cup or bowl, stir together the room temperature buttermilk and the white vinegar.
• With the mixer on low speed, begin to alternate adding the dry ingredient mixture and the buttermilk/vinegar mixture to the main wet ingredient bowl. Start with about one-third of the dry ingredients, mix until just barely combined.
• Add about half of the buttermilk mixture, mix until just combined.
• Repeat with another third of the dry ingredients, then the remaining buttermilk mixture, and finally end with the last third of the dry ingredients.
• Mix on low speed only until just combined after each addition. Scrape down the sides and bottom of the bowl with a rubber spatula to ensure all ingredients are incorporated, but be very careful not to overmix.

6. Bake the Cake Layers:

• Divide the prepared batter evenly between the two prepared cake pans. Smooth the tops gently.
• Bake for 25–30 minutes, or until a wooden skewer or toothpick inserted into the center of each cake layer comes out clean or with a few moist crumbs attached.
• Let the cakes cool in the pans on wire cooling racks for 10 minutes.

7. Cool Completely and Frost:

• After 10 minutes, carefully run a thin knife around the edges of the pans if needed, then invert the cake layers onto the wire cooling racks. Peel off the parchment paper.
• Let the layers cool completely (at least 1-2 hours) before attempting to frost.
• Once completely cool, frost the cake layers with your favorite cream cheese frosting (recipe for frosting not included in this text, but it’s the classic pairing). Assemble as a two-layer cake.
• Slice and serve!