Preheat the oven to 350 degrees Fahrenheit and grease a 9 x 5-inch loaf pan with nonstick cooking spray and line it with parchment paper. Set aside.

In a large bowl, whisk together all-purpose flour, instant pistachio pudding, baking powder, and salt.

In the bowl of a stand mixer or a large bowl, cream together softened butter and granulated sugar until light and fluffy, about 3-4 minutes.

Add eggs one at a time, blending well after each addition. Add almond extract and buttermilk and beat until combined.

Add the dry mixture to the wet mixture and mix until just combined.

Remove 1 cup of the batter and place it in a small bowl. Mix cocoa powder with hot water until smooth. Pour the cocoa mixture into the 1 cup of batter and mix until just combined.

Alternate the two batters in the loaf pan, starting with the pistachio batter. Add ⅓ of the batter to the bottom of the pan. Dollop half of the chocolate batter on top. Repeat with another ⅓ of the pistachio batter and the remaining half of the chocolate batter. Finally, add the remaining ⅓ of the pistachio batter.

Use a knife or skewer to swirl the batter together by dragging the knife through the pan in a zig-zag motion. Turn the pan 90 degrees and repeat.

Top the batter with chopped pistachios and bake for 55-60 minutes, or until the top springs back when pressed and a toothpick comes out clean.