How to Make It
Heat oven to 350°F with racks in upper and lower thirds. Whisk the flour, salt, baking soda, baking powder, and 3 teaspoons cinnamon in a medium bowl until combined.
Beat the butter, sugar, and oil in a large bowl with an electric mixer on medium-high speed until light and fluffy, about 2 minutes. Add the pumpkin puree and mix until combined. Add the eggs, one at a time, and vanilla and beat until combined. Reduce mixer speed to low and slowly add the flour mixture. Beat until just combined.
Combine the pecans, brown sugar, and remaining 1 teaspoon cinnamon in a small bowl.
Rinse and dry the pumpkin can. Lightly coat 3 15-oz cans (or the pumpkin can and a 8½-by-4½ inch loaf pan with nonstick spray; dust with flour, shaking out excess. Add about ⅓ cup batter to the can and sprinkle with about 1 tablespoon of the pecan mixture; use a knife to swirl together. Repeat three times, until each can is about ⅔ full, ending with streusel on top (do not swirl). Pour half of the remaining batter into the prepared loaf pan, sprinkle with half of the remaining streusel. Top with remaining batter and streusel.
Bake both the can and the loaf on bottom rack until the streusel is crisp and golden brown and a toothpick inserted in the center comes out clean, 50 to 55 minutes. Cool in the can for 15 minutes, then slide out and cut into rounds.