Preheat oven to 350 F. Spray a 9 x 9-inch baking dish with baking spray.
Using a large bowl, whisk together flour, baking powder, salt, sugar & spices.
In a medium bowl, whisk together applesauce, milk, melted butter, vanilla & grated carrots. Gradually whisk the wet ingredients into dry ingredients; scrape batter into baking dish.
In a small bowl, whisk together white & brown sugar & either chopped walnuts or whole pepita seeds. Sprinkle over batter. Carefully pour the hot water over the top.
Bake for 45-55 minutes or until middle is set. After removing from oven, allow to cool for 10 before serving with ice cream or whipped cream.