Peel and core pear. Mash the pear and bananas together. Stir in vanilla, rum and buttermilk. Set aside.
Whisk flours, salt, baking soda together in a bowl and set aside.
Cream butter and sugars together with an electric mixer on medium-high speed until light and fluffy, 3 to 5 minutes. Add the eggs one at a time, beating well after each addition.
Reduce the mixer speed to low. Beat in half the flour mixture until just incorporated, followed by one-third of the banana mixture, continue to alternate until all ingredients are incorporated and the batter looks thick and chunky. Be careful not to over mix.
Pour the batter into a prepared 9 inch springform pan. Top with chopped pecans.