Step 1

Adjust oven rack 6 inches from top of oven and heat oven to 375 degrees. Heat maple syrup, cream and ½ teaspoon salt in medium saucepan over medium heat until simmering, about 5 minutes. Off heat, whisk to combine, then transfer to heatproof 2-cup liquid measuring cup.

Step 2

Whisk flour, sugar, baking powder, and remaining ½ teaspoon salt together in large bowl. Whisk milk, eggs, and vanilla in second bowl until combined. Whisk milk mixture into flour mixture until combined. Add melted butter and whisk until smooth. Transfer batter to 8-inch square baking dish set in rimmed baking sheet and spread into even layer with spatula. Pour syrup mixture slowly down corner of baking dish so it flows gently over top of cake batter.

Step 3

Bake until deep golden brown and toothpick inserted in center of cake layer comes out clean, 30 to 35 minutes. Let cool on wire rack for 10 minutes. Use serving spoon to scoop onto plates, inverting each spoonful so sauce is on top.