Preheat your oven to 350°F (180°C). Grease two 8-inch cake pans and line the bottoms with parchment paper to prevent sticking.
In a large bowl, whisk together milk, yogurt, and vinegar. Let it sit for a few minutes until it curdles slightly this helps the cake rise and stay tender.
Mix sugar, vegetable oil, and vanilla extract into the curdled milk mixture until the sugar mostly dissolves. Stir in the red food coloring, adjusting the amount to get your desired shade.
In a separate bowl, whisk together flour, cocoa powder, cornstarch, baking soda, and salt. This ensures even distribution and a smooth, lump-free batter.
Gently fold the dry ingredients into the wet ingredients until just combined. Be careful not to overmix, or the sponge may become dense.
Pour the batter evenly into the prepared pans. Tap the pans gently on the counter to remove air bubbles. Bake for 30–40 minutes, or until a toothpick inserted in the center comes out clean and the cakes feel set to the touch.
Let the cakes cool in the pans for 30 minutes, then carefully invert them onto a wire rack to cool completely. If you plan to assemble the cake the next day, wrap the cooled cakes tightly in plastic wrap to keep them moist.
Trim a thin layer from the tops of the cakes to make them flat. Using a serrated knife, slice each cake horizontally to create two even layers per cake, giving you four layers in total. Reserve the trimmings for decoration if desired.