Generously grease a 10 inch tube or bundt pan with butter
Fill a large pot or wok with enough water for steaming. Put steamer rack or tray in the water (or use a trivet or tuna fish can with ends removed) in center of pan. Make sure your baking pan will fit easily down inside 'steamer'.
Heat water to boiling.
Whisk together: 1 3/4 C. Summers Sprouted Spelt Flour, 1 Tbsp. baking powder, 1 1/2 tsp. cinnamon, 1 tsp. baking soda, 1/4 tsp. sea salt
Add and mix until smooth: 2-3 mashed, ripe bananas (appx. 2 c.), 1 c. maple sugar or Sucanat, 1/2 c. yogurt, 5 egg yolks, 2 Tbsp. soft or melted butter, 1 Tbsp. vanilla extract
Beat 5 egg whites until stiff.
Fold egg whites into the batter & immediately pour into the baking pan.
Place pan in steamer above boiling water. Check water level every 15 minutes & add more boiling water if necessary.
Cover & steam over high heat for 50 minutes or until cake is springy to touch.
Remove cake from steamer & allow to cool slightly.
Unmold onto platter & cut into slices. Serve warm or cold. To reheat, steam 8-10 minutes.