Place the flaked almonds in a large bowl and cover with plenty of boiling water. Set aside for at least half an hour to soak then drain well.
Place the drained almonds in a blender or food processor along with the lemon juice, olive oil, water, salt, garlic and nutritional yeast.
Blend at a high speed until very smooth and creamy. Scrape down the sides as needed to make sure that there are no lumps of almond left. If you need to you can add a drop more water but try not to add too much. If your blender has a tamper tool then I recommend using it! Place the cheese in a covered bowl and refrigerate until needed.
To make the pastry, mix the flour, cornmeal and salt together in a bowl. Add the cold, cubed butter and rub it in using your fingertips until the mixture resembles fine breadcrumbs and no lumps of butter remain.
Gradually stir in enough ice cold water to bring the pastry together into a ball. Wrap and refrigerate for 30-45 minutes until it is firm enough to roll out. Do not let it get too cold however or it will crack.
Roll out the chilled pastry on a floured sheet of baking parchment into a large round, about 33cm wide.
Spread the almond cheese over the pastry, leaving a border of about 5-7cm.
Dot the cheese with blobs of pesto and arrange the tomatoes on top.
Fold the exposed pastry edges over the filling towards the centre of the galette, pleating the edge to make it fit. No need to worry too much about making it look neat - rustic remember!
Slide the sheet of baking parchment onto a baking sheet. Drizzle the tomatoes with a little extra virgin olive oil and sprinkle with herbs. Brush the pastry border with a little non-dairy milk.
Place the galette in the fridge to chill for 30 minutes while you preheat the oven to 200°C/180°C fan/400°F/gas mark 6.
Bake the galette for 45 minutes until it is crisp and golden.