Preheat the oven to 350°. Place the apples, maple syrup and cinnamon in a baking dish, stir well and bake in the oven for 20 minutes.
Grease a 10-inch round springform pan and line with parchment paper. In a mixer, beat the butter with the sugar until light and fluffy.
With the mixer on low, add the eggs one by one. Once incorporated, add the vanilla extract and ground almonds and stir.
Sift the flour and baking powder together in a small bowl and fold into the batter. Pour the batter into the springform pan and push the apples and the pan juices into and over the batter.
Bake the cake for 30 minutes, remove from oven and lower the heat to 325°.
Melt the butter in a pan and stir in the brown sugar, orange zest and almonds. Spread evenly over the cake and bake for 1 hour. Remove from the springform and let cool to room temperature.