Lemon Poppy Seed Streusel Loaf with Crumb Topping

Streusel:

• ¼ cup (31 grams) all-purpose flour
• 2 teaspoons (8 grams) granulated sugar
• 1 teaspoon (3 grams) poppy seeds
• 1½ tablespoons (21 grams) cold unsalted butter

Batter:

• 1¼ cups (250 grams) granulated sugar
• 3 tablespoons (9 grams) lemon zest
• ½ cup (113 grams) unsalted butter, softened
• 3 large eggs (150 grams), room temperature
• ½ teaspoon (2 grams) vanilla extract
• 2¼ cups (281 grams) all-purpose flour
• 1½ tablespoons (13.5 grams) poppy seeds
• 2 teaspoons (10 grams) baking powder
• ½ teaspoon (1.5 grams) kosher salt
• ½ cup (120 grams) whole buttermilk, room temperature
• 2 tablespoons (30 grams) fresh lemon juice

• For the streusel: In a medium bowl, whisk together the flour, sugar, and poppy seeds. Cut in the cold butter using a pastry cutter or two forks until the mixture is crumbly. Refrigerate the streusel until ready to use, at least 30 minutes.
• Preheat the oven to 375°F (190°C). Spray an 8½ x 4½-inch loaf pan with baking spray that contains flour. Line the pan with parchment paper, allowing excess to extend over the sides for easy removal.
• For the batter: In a large bowl, rub the lemon zest into the sugar with your fingers until the mixture is fragrant. Add the softened butter and beat with a paddle attachment or by hand until light and fluffy, about 3 to 4 minutes, scraping the bowl as needed. Add the eggs one at a time, beating well after each addition, then beat in the vanilla.
• Whisk together the flour, poppy seeds, baking powder, and salt in a medium bowl. In a small bowl, combine the buttermilk and lemon juice. With the mixer on low, add the flour mixture to the butter mixture alternately with the buttermilk mixture, beginning and ending with the flour mixture. Mix just until combined after each addition. Spread the batter into the prepared pan and firmly tap the pan on a towel-lined counter to settle the batter. Sprinkle the chilled streusel evenly over the top.
• Bake for 20 minutes at 375°F (190°C). Then lower the oven temperature to 350°F (180°C) and continue baking until a wooden pick inserted into the center comes out with a few moist crumbs and an instant-read thermometer registers at least 205°F (96°C), about 50 to 55 minutes more. Cool the loaf in the pan for 15 minutes, then remove and cool completely on a wire rack. Store in an airtight container for up to 3 days.