Rhubarb Strawberry Pudding Cake

INGREDIENTS

• 1/2 cup whole milk
• 1/2 teaspoon salt
• 1/4 cup water
• 1 1/2 teaspoons cornstarch
• 1 stick (1/2 cup) unsalted butter, melted and cooled slightly
• 1/3 cup plus 1/2 cup sugar
• 2 cups chopped fresh rhubarb stalks (10 ounces)
• 1 cup chopped fresh strawberries (5 ounces)
• 1 teaspoon pure vanilla extract
• 1 3/4 teaspoons baking powder
• 1 large egg
• 1 cup all-purpose flour