2 cups gf flour 1-1/2 teaspoons baking soda 1/2 teaspoon cinnamon 1/4 teaspoon salt 1 cup sugar 1 cup vegetable or canola oil 3 eggs 1 teaspoon vanilla 1/2 cup buttermilk 2 mashed bananas
For frosting: 2/3 cup water 1-1/2 cups sugar 1/4 cup light corn syrup 2 sticks cold unsalted butter, cut into 1/2" slices 4 ounces bittersweet gf chocolate, cut into pieces, and cooled to room temperature 1 teaspoon vanilla extract
Heat oven to 350 degrees F.
Grease a 13"x9" rectangular pan.
In a small bowl, combine flour, baking soda, cinnamon and salt; set aside.
In a large bowl, beat sugar and oil on high speed. Beat in eggs and vanilla. Gradually beat in flour mixture alternating with buttermilk until batter is smooth. Mix in bananas.
Pour batter into prepared pan. Bake for 30-35 minutes or until an inserted toothpick comes out clean. Cool completely before frosting.
For frosting: Pour water into a heavy saucepan and stir in sugar and corn syrup, stirring until sugar has completely dissolved. Set pan over moderately high heat and boil to soft ball stage at 235 degrees F.
Pour hot syrup into a large bowl and beat with an electric mixer at moderately high speed. Add a piece of butter and continue whipping until it has been absorbed then add another piece. Continue until all butter has been added. Whip in cool, melted chocolate and vanilla; continue whipping until frosting is smooth.