Instructions

• Preheat the oven to 350°F (175°C). Spray a 9×5-inch loaf pan with nonstick spray and set it aside.
• In a medium bowl, whisk together 1-1/2 cups (170 g) all-purpose flour, 1 teaspoon baking soda, 1 teaspoon kosher salt, and 1 teaspoon ground cinnamon. Set the dry mixture aside.
• In the bowl of an electric mixer fitted with the paddle attachment (or in a large bowl with a hand mixer), place 3/4 cup (160 g) brown sugar and 1/2 cup (113 g) unsalted butter at room temperature.
• Cream the brown sugar and butter on medium speed until the mixture is lighter in color and fluffy in texture, about 2–3 minutes. Stop once it's light and aerated.
• Scrape down the sides and bottom of the bowl with a spatula. Add 1 large egg, 1 cup (227 g) unfed sourdough starter discard, 1 cup (227 g) mashed ripe banana, and 2 teaspoons vanilla bean paste (or vanilla extract).
• Mix on low speed just until the wet ingredients are combined and uniform in color—do not overmix.
• With the mixer on low, gradually add the flour mixture to the wet mixture. Mix only until the batter comes together and no streaks of flour remain. Stop as soon as combined.
• Pour or scrape the batter into the prepared 9×5-inch loaf pan and smooth the top with a spatula.
• Bake in the preheated oven for 60–75 minutes, until a toothpick inserted in the center comes out clean or an instant-read thermometer inserted into the center reads 200–205°F (93–96°C).
• Remove the loaf from the oven and let it cool in the pan on a wire rack for about 10–15 minutes. Then remove the bread from the pan and allow it to cool completely on the rack before slicing.