Preheat oven to 350°.
Coat a 9-inch round cake pan with cooking spray; line bottom with wax paper. Coat wax paper with cooking spray.
Drain pineapple in a colander over a bowl, reserving 1 tablespoon juice.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, baking powder, baking soda, and salt in a bowl, stirring with a whisk.
Combine granulated sugar, butter, vanilla, and egg in a large bowl; beat with a mixer at medium speed until well blended.
Add flour mixture and buttermilk alternately to sugar mixture, beginning and ending with flour mixture. Stir in pineapple and pecans. Pour batter into prepared pan.
Bake at 350° for 30 minutes or until a wooden pick inserted in center comes out clean.
Cool in pan 10 minutes on a wire rack; remove from pan. Carefully peel off wax paper. Combine powdered sugar and reserved 1 tablespoon juice, stirring with a whisk; drizzle over cake.