Preheat the oven to 350°F (180°C). Grease two 8" or 9" cake pans and set them aside.n2. In a large bowl, mix the oil and sugar together.n3. Beat in the eggs until well combined.n4. Add the gluten-free flour, salt, baking powder, milk, and vanilla, mixing on medium speed until fully combined.n5. Gently fold in the sprinkles.n6. Divide the cake batter evenly between the prepared pans and smooth the tops.n7. Bake for 30-35 minutes or until a toothpick inserted into the center comes out clean.n8. Let the cakes cool in the pans for about 5 minutes before transferring them to a rack to cool completely.n9. For the buttercream, beat the softened butter until light and fluffy, then gradually add powdered sugar and a tablespoon of milk. Mix until smooth and creamy.n10. Once the cakes are completely cool, frost the top of one layer, add the other layer on top, and frost the top and sides of the cake as desired.