1-First Step: Prep and mise en place
Preheat the oven to 350°F and position the rack in the lower third of the oven. Grease a standard 9×5-inch loaf pan with nonstick spray or butter and line with parchment if you like easier removal.

Measure and set aside your dry ingredients: flour, baking soda, salt, and cinnamon. Mash your ripe bananas until mostly smooth. Let the eggs and yogurt or sour cream sit at room temperature for a few minutes if they are cold.

2-Second Step: Combine dry ingredients
In a medium bowl, whisk together the dry mix: 2 cups all-purpose flour, 1 teaspoon baking soda, 1/4 teaspoon salt, and 1/2 teaspoon ground cinnamon. Whisking now helps distribute the leavening and spice evenly so you won’t get pockets of baking soda or cinnamon later.

3-Third Step: Cream butter and brown sugar
With an electric mixer fitted with the paddle attachment, beat 1/2 cup softened unsalted butter and 3/4 cup packed light or dark brown sugar on medium-high speed until the mixture is light and creamy, about 3 minutes. This step adds air and gives a fluffy lift to your loaf.

4-Fourth Step: Add eggs and wet ingredients
Add the 2 large eggs one at a time, mixing well after each addition and scraping down the bowl as needed so everything combines evenly. Beat in 1/3 cup plain Greek yogurt or full-fat sour cream, 1 teaspoon pure vanilla extract, and 1 and 1/2 cups mashed bananas until thoroughly combined.

5-Fifth Step: Combine wet and dry
Reduce the mixer speed to low and add the dry ingredients to the wet mixture. Mix until just combined; overmixing can make the crumb tough. If using the optional add-ins, gently fold in 3/4 cup chopped pecans or walnuts or 1 cup semi-sweet chocolate chips now.

6-Sixth Step: Bake
Pour the batter into your prepared loaf pan and spread evenly. Bake at 350°F for 60 to 65 minutes. To prevent over-browning, loosely cover the top with foil halfway through baking. The loaf is done when a toothpick inserted into the center comes out clean or with moist crumbs. If using a dark metal pan, start checking about 55 minutes in.

7-Final Step: Cool and serve
Cool the loaf in the pan on a wire rack for 1 hour, then carefully remove it from the pan and let it cool completely before slicing. This resting time finishes the crumb and makes slicing tidy. Store wrapped at room temperature for up to 3 days or refrigerate up to 1 week.