Preheat & Prep: Heat oven to 350°F (175°C). Grease and flour loaf pan. Toast and chop walnuts if using.
Cream: In a large bowl, cream butter and sugar until fluffy.
Add Wet: Add mashed bananas and eggs. Mix until blended.
Combine Dry: In a medium bowl, whisk flour, baking soda, and salt.
Combine All: Add dry ingredients to wet. Mix until just combined. Do not overmix.
Add Extras: Stir in vanilla. Fold in walnuts and raisins if using.
Bake: Pour into pan. Bake 55-65 minutes, or until a toothpick comes out clean. Tent with foil if top browns too fast.
Cool: Rest in pan 10 minutes. Remove to wire rack to cool completely.