Preheat oven to 350 degrees and spray a 9x5 loaf pan with non-stick spray.

In a medium bowl, sift and whisk together gluten-free flour, xanthan gum, baking powder and salt. Set aside.

In the bowl of a stand mixer, cream together butter and sugar. Beat in the vanilla paste and add the eggs one at a time.

Mix in the dry ingredients and mix until just combined, scraping the bowl as necessary. Mix in the heavy cream.

In a medium bowl, mix together the cocoa powder, hot water and chocolate extract until smooth. Add 1/3 of the cake batter to the bowl and gently stir until the chocolate is completely incorporated.

To assemble the cake, start by creating a checkerboard pattern in the bottom of the pan by spooning dollops of each batter on opposite sides of the pan. (See example here)

For the second layer, alternate the pattern, spooning vanilla batter over the chocolate and chocolate over the vanilla. Use a knife to run a figure eight pattern through the batter several times to swirl the layers together.

Bake at 350 degrees for 50-65 minutes or until cake tester comes out clean. Oven temps vary so check it after 50-55 minutes. My pound cake took a full 60 minutes to bake. Cool in the pan for 20 minutes before cooling completely on a wire rack.