- Preheat oven to 350F (175C). Lightly grease a 6-quart cast iron pot. 
- In a medium bowl, whisk together flour, baking soda, and salt. 
- In a separate large bowl, cream together the softened butter and sugar until light and fluffy. 
- Beat in the eggs one at a time, then stir in the vanilla extract. 
- Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix. 
- Fold in the mashed bananas and nuts (if using). 
- Pour batter into the prepared pot. 
- Cover the pot with its lid. 
- Bake for 45 minutes, then remove the lid and bake for an additional 10-15 minutes, or until a toothpick inserted into the center comes out clean. 
- Let cool in the pot for 10 minutes before transferring to a wire rack to cool completely. 
- Slice and serve. 
- Optional Tips: For a richer flavor, brown the butter before creaming it with the sugar. Add a teaspoon of cinnamon to the dry ingredients for a warmer spice profile. If the top of the bread browns too quickly, tent it with foil during the last 15 minutes of baking. Substitute gluten-free all-purpose flour blend for a gluten-free option.