Method

• Preheat the oven to 350°F (177°C) with a rack in the center position. Lightly grease a 9-inch (23 cm) round cake pan or an 8-inch (20 cm) square baking pan using a small amount of the measured vegetable oil. Spread the oil evenly across the bottom and sides to help prevent sticking during baking.
• In a medium mixing bowl, combine 2/3 cup (80 g) flour, 2/3 cup (131 g) granulated sugar, 1/4 cup (28 g) chopped pecans, 1 teaspoon (2.6 g) cinnamon, and a pinch of salt. Add 4 tablespoons (57 g) melted, slightly cooled butter. Stir with a fork or spatula for 1–2 minutes until the mixture forms small, moist crumbs with no visible dry flour. Set aside at room temperature.
• In a small bowl, combine 1/3 cup (71 g) packed light brown sugar and 1 teaspoon (2.6 g) ground cinnamon. Stir for about 30 seconds until the cinnamon is evenly distributed and no large sugar clumps remain. Set aside; an even mixture creates a consistent cinnamon layer throughout the cake.
• In a large mixing bowl, whisk together 1/3 cup (67 g) vegetable oil, 2 large room-temperature eggs, 1 cup (198 g) granulated sugar, and 1 cup (213 g) pumpkin puree. Add 1 teaspoon (2 g) pumpkin pie spice, 1 teaspoon (6 g) salt, and 1 teaspoon (4 g) baking powder. Whisk for 1–2 minutes until the batter looks smooth and uniformly orange, with no visible streaks of egg or pumpkin.
• Add 1 1/2 cups (180 g) all-purpose flour to the pumpkin mixture. Fold gently with a silicone spatula for approximately 30–60 seconds, stopping when no dry flour remains. The batter should be thick, smooth, and spreadable. Avoid prolonged mixing, which develops gluten and can make the finished cake tough.
• Spread half the pumpkin batter evenly across the prepared pan using a spatula. Sprinkle the cinnamon-brown sugar filling over the batter, covering the surface as evenly as possible. Carefully spread the remaining pumpkin batter over the filling. Drag a butter knife through the layers in several shallow, curved motions to create a light swirl without completely mixing the filling into the batter.
• Scatter the prepared pecan streusel evenly across the top of the batter, breaking apart any oversized clumps with your fingers. Leave small clusters for a textured topping. Gently press the crumbs into the surface so they adhere during baking, but avoid pushing them deeply into the batter.
• Place the pan on the center oven rack and bake at 350°F (177°C) for 40–45 minutes. The topping should appear golden brown, the edges should look set, and the center should spring back lightly when touched. Insert a toothpick into the center, avoiding a concentrated streak of cinnamon filling; it should come out clean or with a few moist crumbs, not wet batter. If necessary, continue baking in 3–5-minute increments.
• Remove the cake from the oven and place the pan on a wire cooling rack. Let it cool for at least 20 minutes to allow the crumb to firm up as steam escapes and the starch structure sets. Cut into 12 even slices using a sharp knife. Serve slightly warm or at room temperature, when the pumpkin crumb is tender and the pecan topping has a lightly crisp texture.