Preheat oven to 350*F and spray two heart cake pans (OR one pan and reuse it, that's what I did) with nonstick spray.
Whisk together flour, cocoa powder, and baking soda in a bowl and set aside.
In another bowl, combine oil, sugar, and vanilla. Mix on medium speed with an electric mixer until smooth. Add the eggs and mix well.
Add half the flour mixture and half the buttermilk; mix until just combined. Repeat with remaining flour and buttermilk; mix until completely combined.
Stir in 2 tsp pink food coloring, or add more until it's the shade you want. Divide the batter between the two pans (or pour half in the pan if you only have one) and bake 25 minutes, or until a toothpick inserted into the center comes out clean. (If you're doing one pan at a time, bake for about 18 minutes and test it.)
Let cakes cool in pans for 10 minutes, then transfer to a wire rack to cool completely.