Preheat your oven to 180°C (350°F). Grease your cake pan and lightly dust it with flour to prevent sticking.
In a large mixing bowl, sift together the flour, cocoa powder, baking soda, and salt. Set this dry mixture aside to combine later.
In a separate bowl, use an electric mixer to cream the softened butter and sugar until the mixture is pale, fluffy, and fragrant, about 3-4 minutes.
Add eggs one at a time, beating well after each addition to ensure they are fully incorporated and the mixture is smooth.
Gradually add the dry ingredients and buttermilk alternately to the wet mixture, starting and ending with the dry ingredients. Mix gently after each addition until just combined.
Stir in the red food coloring and vanilla extract until the batter is vividly red and well-colored. The batter should be thick but smooth.
Pour the batter into your prepared cake pan, spreading it evenly with a spatula or the back of a spoon. Gently tap the pan on the counter to release any air bubbles.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean and the edges pull slightly away from the pan.
Remove the cake from the oven and let it cool in the pan for about 10 minutes. Then, transfer it onto a wire rack and cool completely before frosting or serving.
Once cooled, slice to reveal the deep crimson interior and enjoy this rich, tender cake with your favorite frosting or simply as is for a dramatic presentation.
