Sift the flour and baking powder into a bowl and add the salt and sugar and mix. Mix the oat milk, beechnut oil, vanilla pulp and lemon juice in a separate container. Add the oat milk mixture to the flour mixture and mix until smooth. Put the dough in the fridge for 20 minutes and preheat the oven to 180°C in the meantime. Thinly brush the madeleine molds with grease and divide the batter among the molds. They should be ¾ filled with batter. Bake in the preheated oven for 15-18 minutes (depending on the baking dish). When the madeleines start to turn slightly golden on the surface, remove the mold from the oven, turn out onto a cooling rack and let cool completely.