Place the vegan butter and sugar in a bowl, and beat with a stand mixer or egg beater (or by hand) until creamy.
Now to create an egg yolk replacement. In a small bowl, combine your flax egg (1 tbsp ground flaxseed with 3 tbsp water) with the soy flour and melted coconut oil.
Add the soy cream and the flax egg mixture to the butter+sugar mixture, one tablespoon at a time, and beat after each addition.
Mix in the vegan quark, vanilla extract, lemon juice and lemon zest, and beat well. Add the vanilla pudding powder and mix.
In a separate, large bowl, add the aquafaba (which is replacing the egg whites) along with the cream of tartar (or use vinegar, see Notes), and beat with an egg beater for a couple of minutes until stiff.
Fold the aquafaba into the batter until mixed.
Pour the batter into the prepared pan and smooth out the top.
Bake for 1 hour, until the edges have pulled away and the top is lightly golden.
Turn off the oven, open the oven door a crack and leave the cheecake for 10 minutes.
Remove from the oven and let cool until it reaches room temperature, about 1 hour.
Refrigerate for 2 hours so that it can set.
Before serving, remove it from the fridge to get to room temperature again.
To get clean slices: take a sharp chef's knife and dip it in ¼a mug of hot water. Wipe it dry with a clean dish cloth, then carefully slice, and repeat.
Serve with berries and whipped (vegan) cream.