Preheat oven to 350 degrees F/180 degrees C . Grease a rectangular loaf tin and line it with a sheet of baking paper, so that the paper hangs on two sides.
In a medium bowl combine all purpose flour, spelt flour, baking soda, cinnamon and nutmeg. Mix well to blend.
Mash the bananas with a fork and transfer them to a large mixing bowl. Add eggs and sugar. Beat with an electric mixer at high speed for 3-5 minutes, until the mixture increases its volume.
Add melted butter and beat shortly until combined. Add yogurt and vanilla and beat for few seconds with the mixer at lower speed, until absorbed in the batter.
Using a rubber spatula, fold the dry ingredients into the batter. Mix gently, just until absorbed.
Pour half of the batter into the prepared pan. Spoon the cream cheese filling in the middle of the pan, avoiding the sides. Pour the rest of the batter to cover the filling. Optionally leave just a bit of the filling to cover the top of the bread.
Bake for 40-50 minutes with the rack at the lower part of the oven. Test for readiness using a toothpick: if it comes out clean, the bread is ready. In case the top starts becoming dark but the bread is still not ready, cover it with a sheet of baking paper or aluminium foil, to prevent burning.
Let the Cream Cheese Banana Bread cool completely inside the pan. Carefully run a knife around the edges and then invert it on a serving plate.
In a medium bowl beat all ingredients with an electric mixer until smooth.
You can make a Double Cream Cheese Banana Bread by covering the baked bread with a cream cheese frosting.
Make sure the loaf pan is filled about ⅔ of its capacity. Otherwise some of the batter might leak during the baking (it happened to me).