Prepare the flax egg by stirring 1 tbsp ground flaxseeds in 3 tbsp of hot water. Allow to sit for a minute or so to become jelly.
Add all ingredients for the cheesecake in a mixing bowl and blend until creamy using an electric hand mixer.
Add the pumpkin purée, flax egg, melted butter, sugar, vanilla and lemon juice to another mixing bowl and mix very well.
Combine the flour with salt, baking powder, baking soda and sift into the pumpkin mixture. Sprinkle over ground almonds and the spices and mix until just combined using a whisk.
Layer the cake (see video in the text above):
Spread half of the pumpkin cake batter into a greased 7-inch round baking tin. Dollop half of the cheesecake mixture over the pumpkin batter. Top with remaining pumpkin batter, and dollop with remaining cheesecake mixture. Carefully, smooth out a bit.
Bake for about 50 minutes. Afterwards, turn off the oven and let the cake in the oven for 10-20 minutes longer. Then, let cool completely.
Blend all ingredients for the frosting using an electric hand mixer.
Spread frosting over cooled pumpkin cake. Place in the fridge to firm up for at least 1 hour before serving.
Decorate with chopped hazelnuts and pecans or other toppings you like.
Instead of all purpose flour or spelt flour, you could make this cake gluten-free by using a gluten-free flour blend 1:1
You can use canned pumpkin purée or make your own according this recipe. If your purée is a bit too wet then put it in a strainer so any excess water can run off.