For the Cake:

1. Preheat the oven to 350°F and grease a 9-inch spring form pan (alternatively, you can use an 8 x 8 baking dish).
2. In a large bowl, whisk together the melted butter, sugar, and vanilla until smooth.
3. Add in the spices, baking powder, and salt and whisk until combined.
4. Add the eggs and mix until thoroughly combined.
5. Add half the flour and mix until just combined. Add in the milk and mix. Add the remaining flour and stir until the flour is just mixed in (avoid the temptation to overmix the batter!).
6. Pour the cake batter into the prepared pan and smooth out the top.
7. Top the batter with a layer of the sliced peaches. Scatter the blueberries evenly over the peach layer.

For the Crumble:

1. In another bowl, stir together the flour, sugar, cinnamon, and salt.
2. Using your fingers, mix the butter into the other ingredients until the mixture is moist, crumbly, and sticks together when pinched between two fingers.
3. Sprinkle the crumble over the blueberries evenly. Place the pan on a baking sheet and place in the oven.
4. Bake for 50-55 minutes or until the top is golden and crisp and a toothpick inserted into the center comes out clean.
5. Cool for 15 minutes before unmolding from the spring form pan.
6. Serve warm or at room temperature, dusted with powdered sugar, and topped with ice cream or whipped cream (as desired!).