Add flour and coconut sugar to a bowl. Rub in cold vegan butter until crumbly. Add cold water a little at a time until a dough forms (we used 1 tbsp, but up to 2 tbsp should work depending on your butter). Spelt flour tends to go crumblier than plain flour, so if using that, knead the dough a little to help.
Press into a ball, wrap and chill for 10-15 minutes in the freezer.
Toss finely sliced apples with coconut sugar, cinnamon, and lemon. We used a mandolin to slice the apples, but you can finely slice with a knife.
Preheat oven to 190c/375f fan (if your oven isn't fan forced, bump to 200c/390f).
Lightly grease your cast iron pan.
Roll pastry into a large rough circle, approx 4-5mm thick, and place into a 20cm cast iron pan.
Place apples on top of the dough, either just pouring them in or creating a pattern, then fold pastry over the apples. Rustic is perfect, you can trim a little off if it feels too much for your liking.
Optional: brush edges with plant milk and sprinkle with coconut or raw sugar.
Bake for 45-55 minutes or until golden and bubbling. If it looks like it’s browning too quickly on top, lightly cover with foil (we usually do this around the 20 minute mark).
Remove from the oven and allow to cool for 10 minutes before serving.