1. Preheat the oven to 350°F. Grease an 8x8x2 inch square cake pan or a 9×2 inch round cake pan. The pan must hold 8 cups of volume.

2. Spread 2/3 cup brown sugar on the bottom of the pan and scatter the pieces of butter over it. Place the pan in the oven for 5-7 minutes until the butter melts.

3. Remove from the oven and stir the butter and sugar together, spreading evenly on the bottom. Arrange sliced bananas to cover the bottom. Set aside.

4. In a bowl, stir together the dry ingredients: all-purpose flour, whole wheat flour, baking powder, baking soda, cinnamon, and salt. Set aside.

5. In a large bowl, cream together 1/3 cup butter and ¾ cup sugar. Add eggs and vanilla, mixing to combine. Add Greek yogurt and mashed bananas, and mix again.

6. Turn the mixer on low and slowly add the dry ingredient mixture. Mix just until combined.

7. Pour the batter over the arranged bananas, smooth the top, and bake at 350°F for 30 minutes.

8. Reduce the oven temperature to 325°F and bake for an additional 25-35 minutes, until a toothpick inserted in the center comes out clean.

9. Let the cake cool in the pan completely, or at least until the bottom is just barely warm, before inverting onto a plate.

10. Use a knife to loosen the edges, place a plate upside-down over the pan, and carefully invert the cake onto the plate.

11. To make the caramel glaze, combine butter, brown sugar, heavy cream, and salt in a saucepan. Bring to a boil over medium heat while stirring constantly.

12. Simmer the glaze for 2-3 minutes, then remove from heat and let it sit for 1-2 minutes.

13. Pour 2/3 of the glaze over the banana layer of the cake. Reserve the rest of the glaze for serving.