Preheat oven to 350 degrees
.Grease your favorite coffeecake dish -- an 9 x 13 rectangular glass baking dish works well
.Sift the flour, baking soda and salt into a medium bowl and set aside.Whisk the eggs and vanilla together in a liquid measuring cup with a spout and set aside.
Cream the butter and sugar until light and fluffy.Gradually pour the egg mixture into the butter, while mixing.
Add the bananas {the mixture will be lumpy}.With a rubber spatula, mix in the flour mixture until just incorporated
.Fold in the blueberries and transfer the batter to the prepared pan.Bake until a toothpick inserted into the center of the coffeecake comes out clean, about 25-30 minutes.