To make the Crème Anglaise, combine 1 tablespoon (15 ml) of the oat milk with the cornstarch in a small cup. Mix well and set aside.
In a saucepan, add the remaining ¾ cup (185 ml) of oat milk, the vegan cooking cream, sugar, salt and the cornstarch mixture. Bring to a boil on medium heat, then simmer for 3 minutes on low heat, stirring continuously. Take the pan off the heat and add the vanilla extract and a very small pinch of turmeric. Transfer to a pouring bowl, set aside to cool, then refrigerate before serving.
To prepare the Sour Cherry Layer, preheat the oven to 370°F (175°C) and set an oven rack in the middle position. Line an 7-inch (18-cm) round cake pan with parchment paper and set aside. Place the cherries in the pan, add the sugar and lemon juice and give it a stir. Bake for 15 minutes, until the cherries are juicy and bubbling. Let the cherries cool completely.
While the cherries cool, to make the Gluten-Free Cake, use a wooden spatula to cream the butter with the extra virgin olive oil, sugar, vanilla and lemon zest. Mix it for 1 to 2 minutes, until it starts to get fluffy. It is not necessary for the sugar to be completely dissolved.
In a large bowl, combine the gluten-free flours, xanthan gum, baking powder, baking soda and salt. Mix well.
In a separate bowl, mix the oat milk with the orange juice. Add one-third of the butter mixture and one-third of the milk mixture to the dry ingredients. Gently fold using a rubber spatula. Add the remaining thirds one by one, folding the wet ingredients just enough to combine. Be careful to not overmix the batter.
Pour the batter over the cooled cherries. Spread the batter evenly using a spatula and bake for 25 to 30 minutes. Let it cool in the pan for at least 20 minutes.
To plate the cake, place a wide plate over the cake pan and flip it. Take off the parchment paper and let it cool completely before slicing. Serve with a drizzle of warm or cold Crème Anglaise.
Keep any leftovers refrigerated in an airtight container, for up to 3 days. Crème Anglaise can be made ahead and will keep well, refrigerated in an airtight container, for up to 3 days.