Heat oven to 350 degrees. Butter and flour a 12-cup Bundt pan. In a large bowl, whisk together flour, baking powder, baking soda, and salt. Set aside. In another large bowl, beat butter until smooth. Add sugar and beat for 2–3 minutes until fluffy. Beat in eggs, one at a time, beating well after each addition. Add lemon juice, lemon zest, and vanilla; beat until combined. Beat in flour mixture in 3 additions, alternating with buttermilk. Beat for 2 minutes on medium high. Fold in blueberries. Spoon into the prepared Bundt pan. Bake at 350 degrees for 50 minutes or until a toothpick inserted in the center of cake comes out clean. Cool on a wire rack for 20 minutes. Run a sharp knife around edges of pan. Turn out and cool. In a small bowl, mix together confectioners sugar, lemon juice, and corn syrup until smooth. Drizzle over top of cake and let it roll down the sides. Garnish with lemon zest, if desired.