Gluten Free Strawberry Banana Upside Down Cake

Name: Gluten Free Strawberry Banana Upside Down Cake
Prep time: 15 min
Cook time: 35 min
Total time: 50 min
Cuisine: American
Ingredients: 2/3 Cup Mashed Bananas (2 medium bananas); 1 1/2 Cup Gluten Free 1-to-1 Flour Blend (I use Bob's Red Mill); 1/2 teaspoon Baking Soda; 1 teaspoon Baking Powder; 1/2 teaspoon Cinnamon; 1/2 teaspoon Salt; 1/3 Cup Oil (olive oil or melted coconut oil); 1/2 Cup Sugar; 1/2 Cup Light Brown Sugar; 1 Egg; 1 Egg Yolk; 1 teaspoon Vanilla; 1 pound Fresh Strawberries (sliced); 1/4 Cup Light Brown Sugar; 2 Tablespoon Cornstarch (or Arrowroot Powder)