Preheat the oven to 350 degrees F. Spray a 9-by-4-inch loaf pan with cooking spray.
Combine the bananas, eggs, sugar, coconut oil, yogurt, and rum and vanilla extracts in a bowl.
In another, larger bowl, whisk together the flour, baking powder and salt.
Make a well in the center of the dry ingredients. Pour the wet ingredients into the dry ingredients and stir until the flour is incorporated and batter is smooth. Pour the batter into the prepared loaf pan and bake until golden brown and a skewer inserted into the center of the loaf comes out clean, about 1 hour. Remove from the oven and set aside while you make the glaze.
Melt the butter in a saucepan over medium heat. Add the brown sugar and 1/2 cup water and stir. Cook until the sugar dissolves, and then continue cooking another 3 to 5 minutes over low heat until the mixture bubbles around the edges. Turn off the heat and carefully (in case it flames) stir in the rum and the orange zest.
Slowly pour half of the glaze over the banana bread, allowing it to seep into all the surfaces. Wait until the glaze has been absorbed, about 30 minutes, and then turn the loaf out of the pan.
Slice and serve with vanilla ice cream, if using, and the remaining glaze.