Preheat oven to 350F and lightly grease a round 9-inch cake pan. Set aside.
In a large bowl, whisk mashed bananas, sugar, oil, eggs, yogurt, and vanilla until smooth. In a separate medium bowl, whisk flour, baking soda, spices, and salt until combined.
Fold flour mixture into liquid until batter is just combined. Scrape into prepared pan and smooth top.
Walnut Streusel
Combine all streusel ingredients in a small bowl until crumbly. Sprinkle evenly over batter.
Bake cake at 350F 45-50 minutes until a toothpick inserted in center comes out clean. Cool cake completely on a wire cooling rack before cutting into squares. Enjoy!
Notes
Storing InstructionsStore cake in an airtight container at room temperature up to 4 days. Cake may also be frozen up to 2 months.