Preheat oven to 350°.
Bring syrup to a boil in a medium nonstick skillet over medium-high heat; cook 2 minutes. Remove from heat; arrange pears in pan in a spokelike fashion. Place pan over medium-high heat, and cook until syrup thickens (about 4 minutes), gently shaking pan frequently.
Lightly spoon flour into a dry measuring cup; level with a knife. Combine flour and next 4 ingredients (flour through salt); stirring well with a whisk. Place sugar, butter, and vanilla in a large bowl; beat with a mixer at medium speed until well-blended (about 2 minutes). Add eggs, 1 at a time, beating well after each addition. Stir in flour mixture alternately with buttermilk, beginning and ending with flour mixture.
Pour batter evenly over pear mixture in prepared pan; wrap handle of skillet with foil. Bake at 350° for 30 minutes or until cake springs back when touched lightly in center. Run a knife around outside edge. Cool in pan 5 minutes. Place a plate upside down on top of cake; invert onto plate. Serve warm.