Preheat your oven to 180°C and line a baking tray with parchment paper.
Mix the flour, sugar and salt in a bowl. Add the vegetable oil and mix until a dough forms. If dough is crumbly, add a bit of water and mix until a smooth dough forms.
Mix all filling ingredients in a bowl.
Spread the dough on the baking tray and shape it like a round.
Fill it with the plums mixture in the center then fold in the edges to create a galette (look at the photos).
Bake in preheated oven for 30-35 mins until golden brown on the edges.