Start by preheating the oven to 350 F. Grease a deep 7" bundt cake pan with shortening or butter. Lightly dust the inside of the bundt pan with 1 tablespoon of flour. I just shake it about, then tip the excess out.
Mix the sugar, eggs, oil, and vanilla in a bowl until light and fluffy, about 5 minutes.
¾ cup vegetable oil, 3 large eggs, 1 teaspoon vanilla extract, 2 cups sugar
In a separate bowl mix the flour, baking powder, and salt. Whisk to blend.
2 cups flour, 1 teaspoon baking powder, ¼ teaspoon salt
Add the flour mixture to the wet ingredients in 3 to 4 portions, mixing well after each addition. Spoon out ⅓ of the batter into a smaller bowl.
Add the sifted cocoa powder to the batter in the small mixing bowl. Blend well.
2 tablespoon cocoa powder
Layer the batter, alternating with half the vanilla batter first, then spoon in the chocolate batter, and top with the remaining vanilla batter. Bake for 40 minutes in prepared oven.
Remove cake from oven, let cool to 8 minutes. Place serving plate on top of the bundt cake pan, then invert to tip out the cake. Let cool completely before decorating.