Banana Upside-Down Cake

INGREDIENTS

• 1/2 teaspoon salt
• 2 eggs
• 3/4 teaspoon baking soda
• 1 1/2 cups cake flour
• 1/2 teaspoon baking powder
• 1 cup firmly packed light brown sugar
• 1 1/4 cups sugar
• 6 tablespoons (3/4 stick) unsalted butter, room temperature
• 1 teaspoon vanilla extract
• 1/3 cup vegetable shortening
• 1/2 cup buttermilk
• 1 cup mashed ripe bananas (about 2)
• 2 large ripe bananas, sliced