Preheat oven to 350°F (177°C). Grease a 9×2-inch round cake pan, line with a parchment paper round, then grease the parchment paper. Parchment paper helps the cake seamlessly release from the pan.
In the bowl of an electric handheld or stand mixer fitted with a paddle attachment, cream the sugar and butter together on medium speed until light and fluffy, about 4-5 minutes. With the mixer on low, slowly stream in the oil. Scrape the sides and bottom of the bowl to make sure everything is well blended. With the mixer on low, add in the eggs, one at a time, making sure that each is incorporated before adding in the next. Add the vanilla and run the mixer for 30 more seconds. Take the bowl out of the mixer.
In a medium bowl, whisk the flour, cocoa powder, baking powder, baking soda, and salt until combined. With a silicone spatula or wooden spoon, fold the flour mixture into the butter mixture in three batches, mixing each until almost blended. Batter will be very thick. Finally, pour in the hot water and whisk to combine. Pour evenly into prepared cake pan. Lightly tap pan on the counter a few times to settle the cake batter and release any trapped air bubbles.
Bake in the center of the oven for 30-36 minutes (and up to 40 minutes, if needed but begin checking at 30). The cake is done when a toothpick inserted into the center comes out clean or when the cake springs back if you lightly poke the center with your finger. Remove from the oven and cool cake in the pan set on a cooling rack for 20 minutes. Remove cake from the pan and place cake directly on the cooling rack to finish cooling. Once cool, you can place the cake on your cake stand or serving plate.