• Preheat the oven to 350 °F. Line the bottom of a 9" square or 9 or 10" round pan with parchment paper or butter and flour the pan.

Topping

• Toss the mango slices with 8 oz brown sugar, finely grated zest and juice from 1 lime. Allow to macerate for 30 minutes to an hour. Drain the mango and reserve the juices.
• Combine the mango juice with 2 oz unsalted butter in a small saucepan and bring the mixture to a boil. Allow to boil for 1-2 minutes to thicken. You should end up with about 1 cup of caramel.
• Pour the warm caramel into the prepared pan. Arrange the mango slices in an attractive pattern onto the caramel. Place the pan in the freezer while preparing the batter.

Batter

• Combine 1 large egg, ¼ cup (2 oz) of the buttermilk, 1 teaspoon vanilla extract and finely grated zest from 1 lime in a small bowl.
• Sift together 6 ¾ oz cake flour, 1 ½ teaspoons baking powder and ¼ teaspoon table salt in a mixing bowl, add 8 oz granulated sugar and 2 oz almond flour. Run the mixer on low speed for 30 seconds to combine the dry ingredients.
• Add 4 oz butter to the dry ingredients and mix until combined. Add the remaining ¼ cup of buttermilk to the flour and butter mixture. Turn the mixer to medium high for 2-3 minutes.
• Turn off the mixer and scrape the bowl and paddle. Add the egg mixture in two batches, scraping between additions.
• Starting from the outer edge of the pan, gently dollop the batter over the mango slices. Spread the batter to an even layer.
• Bake until the center of the cake springs back lightly when pressed, or a toothpick inserted in the center comes out clean, about 30 minutes. Cool in the pan for 15 minutes.
• Unmold the cake while it's still a little warm by running a paring knife around the sides of the cake and inverting onto a serving platter. If any caramel or mango slices stick in the pan scrape them out with a small spatula and replace on the cake while still warm.
• Serve warm or room temperature.