Gluten Free Vanilla Cake – 1/2 cup (110g) unsalted butter, room temp (reg or plant-based) – 1/3 cup (75g) vegetable oil – 1 3/4 cup (350g) granulated sugar, divided – 4 large eggs, room temp – 1 tbsp vanilla extract – 2 1/4 cups (300g) cup for cup gluten free baking flour* – 1/4 cup (30g) cornstarch – 2 tsp baking powder – 1/2 tsp baking soda – 1/2 tsp kosher salt – 1 cup (240g) milk, room temp (reg or plant-based) – 1 tbsp apple cider vinegar Vanilla Buttercream – 1 1/2 cups (340g) unsalted butter, room temp (reg or plant-based**) – 2 tbsp milk, room temp (reg or plant-based) – 1 tsp vanilla extract – Pinch of kosher salt – 5 cups (550g) powdered sugar, spooned and leveled