Instructions

for the cake

Adjust oven rack to middle position and heat oven to 350 degrees. Grease and flour 12-cup nonstick Bundt pan. Combine flour, salt, baking powder, and baking soda in medium bowl. In small bowl, whisk buttermilk, rum, vanilla, and lemon juice together.
Using stand mixer fitted with paddle, beat butter and sugar on medium-high speed until pale and fluffy, about 3 minutes. Add eggs and egg yolk, one at a time, and beat until combined. Reduce speed to low and add flour mixture in 3 additions, alternating with 2 additions of buttermilk mixture, scraping down bowl as needed.

for the streusel

Reserve 2 tablespoons pecans. Use fork to combine remaining pecans, brown sugar, and butter in bowl.
Scrape two-thirds of cake batter into prepared pan, sprinkle with even layer of pecan streusel, and top with remaining batter. Bake until toothpick inserted in center comes out clean, 50 to 60 minutes, rotating pan halfway through baking. Let cake cool in pan on wire rack–lined rimmed baking sheet for 20 minutes.

for the rum syrup

Meanwhile, bring sugar, rum, and water to boil in small saucepan and simmer over medium-low heat until sugar dissolves, about 2 minutes. Whisk in butter until smooth. Let rum syrup cool completely, about 30 minutes. Remove cake from pan and prick all over with fork. Brush warm cake with ¾ cup rum syrup and let cool completely, about 2 hours.

for the glaze

Whisk confectioners’ sugar into remaining rum syrup until smooth. Drizzle glaze evenly over top of cake and sprinkle with reserved pecans. Let sit until glaze is firm, about 30 minutes. Serve.