Preheat the oven to 180°C (350°F). Line the bottom of a 20cm (8-inch) round cake pan that's at least 6cm (2.5-inch) tall with parchment paper. Generously grease the parchment paper and sides of the cake pan.
Add the butter, brown sugar, maple syrup, cinnamon and salt to a small saucepan over medium heat. Mix the ingredients until the butter has melted and the sugar has just dissolved. If the sugar is taking some time to dissolve, add a dash of milk and stir until smooth.
Add the pecans to the caramel, and mix through. Spread the pecan topping evenly over the bottom of the pan. Place the cake pan in the freezer to let the topping set.
In a large bowl, add all the dry ingredients and whisk until well combined. Add all the wet ingredients and mix until just combined.
Pour the batter into your prepared pan on top of the pecans.
Bake the cake for around 48-53 minutes (or 45-50 minutes for a 9-inch pan). If your cake is browning too quickly, carefully tent the pan with aluminum foil. The cake is ready when the surface is a light golden brown, and if you insert a toothpick into the center, it should come out mostly clean (a few moist crumbs are fine).
Let the cake cool in its pan on a wire rack for 10-15 minutes. Place a serving platter on top of the pan and quickly turn the cake upside down. Serve the cake warm or at room temperature.
