1. Preheat oven to 350°.
2. Melt 3 tablespoons butter in a large skillet over medium-high heat. Add brown sugar and bananas; sauté 4 minutes, stirring occasionally. Remove from heat; cool 10 minutes. Place banana mixture in a large bowl. Beat with a mixer at medium speed until smooth.
3. Combine buttermilk and next 3 ingredients (through eggs). Weigh or lightly spoon flour into dry measuring cups; level with a knife. Combine flour, baking soda, and salt. Add flour mixture and buttermilk mixture alternately to banana mixture, beginning and ending with flour mixture; beat at low speed just until combined. Scrape batter into a 9 x 5-inch metal loaf pan coated with baking spray. Bake at 350° for 1 hour or until a wooden pick inserted in center comes out with moist crumbs clinging. Cool for 10 minutes in pan on a wire rack. Remove bread from pan, and cool on wire rack.
4. Melt remaining 1 tablespoon butter in a small, heavy saucepan over medium-high heat. Cook 3 minutes or until butter begins to brown; remove from heat. Add powdered sugar and half-and-half, stirring with a whisk until smooth. Drizzle glaze over bread. Let stand until glaze sets.