How to Make It
Preheat oven to 350°.
To prepare streusel, combine first 5 ingredients in a medium bowl. Add 2 tablespoons melted butter, stirring until well combined. Stir in nuts. Set aside.
To prepare bread, weigh or lightly spoon 9 ounces flour into dry measuring cups; level with a knife. Combine flour, baking soda, baking powder, and 1/2 teaspoon salt in a bowl, stirring well with a whisk. Combine 5 tablespoons butter and granulated sugar in a large bowl; beat with a mixer at medium-high speed until well blended. Add eggs, 1 at a time, beating well after each addition; beat in vanilla. Beating at low speed, add flour mixture and buttermilk alternately to sugar mixture, beginning and ending with flour mixture; beat just until combined. Scrape half of batter into a 9 x 5-inch loaf pan coated with baking spray; sprinkle with half of streusel mixture. Spread remaining batter over streusel; swirl. Sprinkle remaining streusel on top of batter. Bake at 350° for 50 minutes or until a wooden pick inserted in center comes out with moist crumbs clinging. Cool 10 minutes in pan on a wire rack. Remove from pan; cool completely on wire rack.