Preheat oven to 350oF (180oC).Grease and line heart-shaped cake pan (8 x 1.5 inch / 20 x 4 cm) with parchment paper. Set aside. To a bowl, add water, vinegar and sugar. Whisk until sugar is completely dissolved.
Then, add vanilla extract. Mix well.
Add vegetable oil and mix well.
Sift in flour, cocoa powder, baking powder, baking soda and salt.
Mix until dry flour is no longer visible. DO NOT OVER MIX (mix until dry and wet ingredients are just combined).
Add red food coloring gel and mix until combined.
Pour batter into cake pan.Drop pan on table to remove air bubbles. Bake in preheated oven to 350oF (180oC), rack middle position, 30-35 minutes, or until toothpick inserted in the middle of cake comes out clean.
Let cake cool down in pan for 10 minutes. Then transfer cake to wire rack to cool down completely.
Place 2 paper hearts on top of cake and dust with icing/powdered sugar. Then, remove paper hearts.