Preheat oven to 350°F (175°C) with the rack in the center position. Grease a 9x5-inch loaf pan and line with parchment paper, leaving overhang on the long sides to create handles.
Spread 1 cup of chopped pecans on a baking sheet and toast in the oven for 5–8 minutes, stirring once, until fragrant and slightly darker. Remove and let cool completely.
Peel the overripe bananas into a large mixing bowl and mash with a fork until mostly smooth with just a few small lumps, yielding about 1½ cups (345g).
To the mashed bananas, add the melted cooled butter, vegetable oil, granulated sugar, brown sugar, eggs, and vanilla extract. Whisk vigorously for about 1 minute until well combined and slightly lighter in color.
In a separate bowl, whisk together the flour, baking soda, salt, and cinnamon (if using) for about 30 seconds until evenly combined and lump-free.
Pour the dry ingredients into the wet ingredients and fold gently with a rubber spatula just until no streaks of flour remain — do not overmix. The batter will look slightly lumpy and thick.
Gently fold the cooled toasted pecans (reserve the ¼ cup for topping) into the batter using as few strokes as possible to maintain a light, tender texture.
Pour batter into the prepared loaf pan, spread evenly, and tap the pan on the counter 2–3 times to release air bubbles. Sprinkle the reserved ¼ cup of pecans over the top and press lightly to adhere.
Bake for 55–65 minutes, tenting loosely with foil after 30 minutes to prevent over-browning. The bread is done when a toothpick inserted in the center comes out with just a few moist crumbs.
Cool the bread in the pan on a wire rack for 10–15 minutes, then lift out using the parchment handles and cool completely on the rack for at least 1 hour before slicing.