Start by preparing the ingredients first. Cut butter into small pieces, place it into a small bowl and melt in the microwave for 30 seconds at two separate times (so the butter does not react too much in the microwave from prolonged heating). Set aside and let it cool.
Rinse and dice strawberries. Peel bananas, place them into a separate bowl and beat with a hand mixer until smooth.
Sift 4 cups of flour. (Reserve ¼ cup to coat strawberries.) Add salt, baking powder, baking soda and combine with flour. Set aside until ready for use.
Preheat oven to 350 F. Beat eggs and sugar on high for 5 minutes. Reduce beating speed to low and add melted butter, vanilla, and then mashed bananas. Increase the speed to medium and beat for 30 seconds. Reduce the speed to low and add flour, one cup a time.
Add flour-coated strawberries. Mix in the strawberries gently with a spatula.
Pour batter into 2 – 9 x 12 baking pans lined with parchment paper.
Bake 2 pans at the same time at 350 F for 45 min or until golden brown. Check readiness with a toothpick inserted in the center, and comes out clean. Remove from the oven and let the cakes cool for 5 minutes before removing them from pans. Remove cakes from pans, let it cool for 15 minutes before slicing.
Dust each cake with powdered sugar.
Cut into equal 15 pieces. Place each cake onto cupcake liners for a prettier presentation (optional).