Preheat the oven to 350F.

In a large mixing bowl, whisk the eggs and sugar until smooth. Then, add the wet ingredients and stir to combine.

Add the flour, leavening agents, and salt, gently folding to combine. Mix until there are no clumps, but do not overmix. It just needs to barely combine.

Split the batter into two, with one portion being slightly less. To the smaller portion, add the cocoa powder and hot water and mix to combine. Now, you’ll have vanilla and chocolate batters.

Line your 8 or 9-inch loaf pan with parchment paper. For the first layer in the pan, place a scoop of light batter, then dark batter, then light batter. On top of that layer, place another layer of scoops, but alternate so that the vanilla layer is on top of the chocolate layer and vice versa. Follow this pattern until you run out of batter.

With a knife or skewer, carefully run it through the batter in an S-line or zigzag. You only need to run it through a couple of times; otherwise, the batters will blend too much, and it won't have a marbled look anymore.

Bake the marble cake for 45 minutes, then cover it with foil and bake for another 15-20 minutes or until thoroughly baked. It should be springy to the touch and a toothpick inserted into the center will come out clean. Allow it to cool before slicing into it.