Banana Cake with Toffee Sauce

Toffee sauce 1 1/4 cups plus 3 tablespoons (or more) heavy whipping cream

1/2 cup (packed) golden brown sugar

1/2 cup dark corn syrup

1/4 cup (1/2 stick) unsalted butter

Banana cake

2 cups unbleached all purpose flour

1 1/2 teaspoons baking powder

3/4 cup (1 1/2 sticks) unsalted butter, room temperature

2/3 tablespoons (packed) dark brown sugar

2 large eggs

1 cup mashed very ripe bananas (2 to 3)

1 tablespoon dark rum

1 1/2 teaspoons vanilla extract

8x8x2-inch nonstick metal baking pan

Toffee Sauce

Bring 1 1/4 cups cream, brown sugar, corn syrup, butter, and 1/8 teaspoon salt to boil in heavy small saucepan over medium heat, whisking until sugar dissolves. Reduce heat to medium-low and cook at gentle boil until sauce coats spoon thickly and is reduced to 1 1/2 cups, whisking occasionally, about 15 minutes. Remove from heat and cool. Whisk in 3 tablespoons or more cream to thin sauce to desired consistency.  Can be made 2 days ahead. Rewarm slightly before using.

Banana Cake

Preheat oven to 350°F. Butter 8x8x2-inch nonstick metal baking pan. Dust baking pan with flour, tap out excess.

Whisk flour, baking power, and 1/2 teaspoon salt in bowl. Using mixer, beat butter and sugar in large bowl until well blended. Beat in eggs 1 at a time. Beat in mashed bananas, rum, and vanilla (batter may look lumpy). Add dry ingredients in 4 additions, beating just to blend after each addition. Spread batter evenly in prepared baking pan.

Bake cake until toothpick inserted into center comes out clean, 35 to 38 minutes. Spread 1/2 cup toffee sauce evenly over cake. Return cake to oven and bake until sauce is bubbling, about 6 minutes. Cool cake in pan on rack 30 minutes. Cut around cake in pan. Cut cake into squares. Serve cake slightly warm or at room temperature with left over toffee sauce and top with sliced bananas.