1. Preheat oven to 350°F. Spray an 8×8-inch baking pan with cooking spray, line the bottom with parchment paper, and spray the parchment.
2. In a large bowl, whisk together the flour, oats, baking powder, cinnamon, salt, and nutmeg.
3. In a small bowl, whisk together the mashed bananas, egg, Greek yogurt, honey, and vanilla.
4. Pour the wet ingredients into the dry and mix with a rubber spatula until just combined — do not overmix.
5. Pour the batter into the prepared pan and bake for 18–20 minutes, or until a toothpick inserted in the center comes out clean.
6. Cool the cake in the pan on a wire rack for 10 minutes, then remove it from the pan and let it cool completely.

Cinnamon Cream Cheese Frosting

1. In a bowl, beat the softened cream cheese with a hand mixer or stand mixer fitted with the whisk attachment until smooth, about 1 minute.
2. Add the powdered sugar, cinnamon, and vanilla. Whisk until smooth and fluffy, scraping down the sides as needed. If the frosting is too thick, add milk one teaspoon at a time until spreadable.
3. Spread the frosting over the completely cooled cake. Top with chopped toasted pecans if desired.