Preheat & Prep Loaf Pan: Position oven rack in the center and preheat oven to 350°F (175°C). Lightly grease an 8.5x4.5-inch (or standard 9x5-inch) metal loaf pan and line with parchment paper, leaving a 2-inch overhang on the sides for effortless removal.
Whisk Dry Ingredients: In a medium mixing bowl, whisk together the flour, baking soda, ground cinnamon, pumpkin pie spice, and fine sea salt until well combined and lump-free.
Mix Wet Pumpkin Batter: In a large bowl, whisk together the canned pumpkin puree, dark brown sugar, granulated sugar, melted butter, room-temperature eggs, milk, and vanilla extract until glossy and smooth. Pour the dry ingredients into the wet mixture and fold gently with a rubber spatula just until no dry flour streaks remain. Do not overmix.
Prepare Cream Cheese Filling: In a separate clean bowl, beat the softened cream cheese, granulated sugar, egg yolk, flour, and vanilla extract with a hand mixer on medium speed for 1 to 2 minutes until creamy, completely lump-free, and velvety smooth.
Layer & Marble Swirl: Spread two-thirds of the spiced pumpkin batter into the bottom of the prepared loaf pan. Dollop the cream cheese filling evenly across the top, smoothing gently with an offset spatula. Spoon remaining pumpkin batter over the cream cheese layer. Using the tip of a butter knife or skewer, gently swirl in figure-eight motions to create a gorgeous marbled ribbon pattern.
Top & Bake: Stir together the turbinado sugar and cinnamon in a small pinch bowl; sprinkle evenly over the loaf. Bake for 55 to 65 minutes at 350°F (175°C). Tent loosely with aluminum foil at the 35-minute mark if the top is browning too quickly. A wooden toothpick inserted into the pumpkin bread portion should come out clean with a few moist crumbs (avoid testing directly into the molten cream cheese pocket).
Cool & Slice: Let the loaf rest in the pan on a wire cooling rack for 20 minutes. Use the parchment sling to lift the bread out and allow it to cool completely (at least 1 to 2 hours) before slicing. Chilling for 30 minutes in the fridge produces laser-sharp bakery-style swirl slices.