Prepare Pecan-Crumb Topping:In medium bowl, combine 1/3 C. brown sugar, 1/4 C. flour and 1/4 tsp. cinnamon.With pastry blender or 2 knives used scissors-fashion, cut in 2 T. butter until mixture resembles coarse crumbs.Stir in pecans; set aside.
Preheat oven to 350ºF.Lightly grease 13”x9” metal baking pan.
Prepare Banana Cake:In small bowl, mix bananas, lemon juice and vanilla.On waxed paper, mix flour, baking powder, baking soda, cinnamon and ½ tsp. salt. (I sifted all these ingredients together.)
In large bowl, with mixer on medium speed, beat butter and sugars until light and creamy, 5 minutes, scraping bowl often.Add eggs, 1 at a time, beating well after each addition.On low speed, alternately add flour and banana mixtures, beginning and ending with flour mixture; beat until smooth.
Spoon batter into prepared pan and spread evenly.Sprinkle with crumb topping.Bake 25 to 30 minutes or until toothpick inserted in center comes out clean.Cool in pan on wire rack.