How to Make It
Preheat oven to 350ºF. Mist 6 6-oz. ramekins with cooking spray. Place a roasting pan in oven; pour in 1/2 inch of hot water. In a bowl, whisk flour, cocoa and baking powder.
Combine chocolate and butter in a microwave-safe bowl; cook on high, stirring once or twice, until almost melted, 1 to 2 minutes. Whisk until smooth.
In a bowl, with an electric mixer on medium-high speed, beat eggs, vanilla, sugar and salt until pale yellow, about 5 minutes. Beat in melted chocolate mixture. Stir in flour mixture. Spoon half of batter into ramekins. Drop 1 Tbsp. of Nutella into center of each. Cover with remaining batter.
Transfer ramekins to roasting pan. Bake until cakes have risen and are cracked on top, about 30 minutes. Let cool for 5 minutes. Serve warm.