Preheat the oven to 350℉. Butter and flour a 9x5 ceramic or metal loaf pan. In a large bowl, cream the butter and granulated sugar.
Add the mashed bananas and combine.
Add the eggs and vanilla extract and combine.
Add the sour cream, baking soda, and salt and combine.
Add the flour and with a spoon stir to combine until just incorporated.
Stir in the raisins.
In a separate small bowl, combine the ¼ cup granulated sugar and the cinnamon.
Pour half of the banana raisin batter into the loaf pan. Sprinkle the cinnamon sugar mixture over the batter. Top with the remaining batter.
Bake for 55-60 minutes if using a ceramic loaf pan or 50-55 minutes if using a metal loaf pan. The Banana Raisin Bread is done when a toothpick inserted into the middle comes out without any wet batter. See the note above on ensuring that the loaf does not get overdone.
Notes
Choosing Bananas: If you like an intense banana flavor, choose overripe bananas that are more brown than yellow. If you like a strong, but not too intense flavor go with bananas that are between ripe and overripe. These are bananas that have plenty of brown spots but are more yellow than brown. Because this recipe calls for sour cream it will reduce the overall intensity of the banana flavor. See the notes above and the link to my Guide on Baking Banana Bread.
Mashing Bananas: Use a handheld mixer to mash the bananas in a 4-cup measuring cup. Start with 4 medium bananas, then add pieces of a 5th banana if needed. Check to make sure that the mashed bananas are at the 2-cup line. It's an easy way to mash the bananas and will give you a precise measurement for 2 cups.
Loaf Pan Material: A ceramic loaf pan will take 5-10 minutes longer to bake than an aluminum loaf pan. Adjust the timing accordingly. Baking times also vary by oven type. If you want to be precise you can buy a separate oven thermometer to use in the oven and monitor the temperature inside the oven.
Dish Size and Shape: This recipe can be made in a variety of oven-safe dishes. You will just need to adjust the timing. If the dish is shallower and wider it will require less baking time. See baking times for reference below: