Step 1: Prepare the Cake Pans: Preheat oven to 350°F (175°C). Grease two 8-inch heart-shaped cake pans and line with parchment paper.
Step 2: Mix Dry Ingredients: In a medium bowl, whisk together flour, sugar, cocoa powder, baking soda, and salt.
Step 3: Mix Wet Ingredients: In a large bowl, combine vegetable oil, buttermilk, eggs, red food coloring, and vanilla extract. Stir in vinegar last.
Step 4: Combine Ingredients: Gradually add dry ingredients to wet ingredients and mix until just combined. Do not overmix to keep the cake tender.
Step 5: Bake the Cake: Divide batter evenly between the two prepared pans. Bake for 25–30 minutes or until a toothpick inserted in the center comes out clean. Cool cakes in pans for 10 minutes, then remove to wire racks to cool completely.
Step 6: Prepare the Frosting: Beat cream cheese and butter together until creamy. Gradually add powdered sugar, one cup at a time, until smooth. Beat in vanilla extract.
Step 7: Assemble the Cake: Level the tops of the cakes if needed. Place one layer on a serving plate and spread a layer of frosting. Top with the second layer and frost the top and sides of the cake. Decorate with sprinkles, sanding sugar, chocolate hearts, or piped frosting as desired.