If your eggs are not yet at room temperature, set them in a bowl of hot water to warm up.
Preheat the oven to 350 F. Grease and flour a 9 inch cake pan, round or square.
Set the eggs and sugar in a large bowl and use a hand mixer (you can also do this in a stand mixer) to beat. Beat until the mix is several shades lighter in color, is airy and when you lift the beaters from the mix it falls in ribbons - about 3-5 minutes. Add the salt and vanilla and beat to combine.
With the mixer on, slowly pour in the olive oil. Beat until fully combined.
Sift the cocoa into the bowl and beat to combine. Add the flour, baking powder, and baking soda. Start the mixer on low and as you are mixing in the flour, slowly pour in the buttermilk. Once it’s all in, give the bowl a scrape on the sides and bottom and beat to just combine.
If you will not be topping the cake and want to do a sugar crisp: sprinkle 3 tablespoons of granulated sugar on top.
Bake the cake until a cake tester comes out clean, about 40-45 minutes. LEt cool briefly in the pan then transfer to a wire rack or plate to fully cool.