Preheat your oven to 350°F (177°C). Butter a 9 by 5 inch loaf pan, then line it with parchment paper, allowing extra paper to hang over the sides for easy cake removal. Butter the top of the parchment paper as well. Set the prepared pan aside until ready to use.

In a medium bowl, whisk together the cake flour, baking powder, and salt. In a separate small bowl, mix the sour cream and milk until smooth. In yet another medium-sized bowl, combine the Dutch-process cocoa powder with the hot water, stirring until the cocoa is fully dissolved. Set all these mixtures aside for assembly later.

In the bowl of an electric mixer fitted with the paddle attachment, or using a hand mixer, beat the room temperature butter and white sugar for 4-5 minutes, until very light and fluffy. Add the eggs one at a time, beating well after each addition, then add the vanilla extract. Scrape down the sides and bottom of the bowl. With a spatula, stir in the flour mixture from Step 2 alternately with the sour cream and milk mixture from Step 2, mixing only until just combined to avoid overmixing. I always make sure not to overmix at this stage for the fluffiest texture.

Pour about one third of the batter (a little more than 1 cup) into a bowl with the freeze-dried strawberry powder and stir to combine. In another bowl, mix another third of the batter with the cocoa and water mixture from Step 2 until fully combined. Leave the final third of the batter plain in the original bowl. If you like your strawberry layer more vibrant, feel free to add a bit of red gel food dye here. These individually flavored batters will create a fun and colorful marbled effect in your cake.

Spread the strawberry batter into the bottom of the prepared loaf pan. If desired, spread 3 tablespoons of strawberry preserves or jam over the strawberry batter for extra flavor. Next, layer the chocolate batter over the strawberry layer, then top with the plain vanilla batter. Using a butter knife or skewer, swirl the batters together to create a marbled effect, running the tool from side to side and top to bottom, and then repeat after turning the pan. Smooth the top of the batter. Bake in the preheated oven for 50 to 58 minutes, until a cake tester inserted comes out clean. Let the cake cool in the pan on a rack for 10 minutes, then turn it out and let it cool completely on the rack.

In a bowl, stir together the powdered sugar, milk, freeze-dried strawberry powder, and a pinch of salt until smooth. Pour the glaze evenly over the completely cooled cake. I like to drizzle extra glaze over the sides for a decadent finish—don't hold back if you love that sweet-tart strawberry flavor!