Preheat oven to 350°F (180°C). Position the rack in the center. Line a cupcake pan with paper liners; set aside.
In a medium mixing bowl, combine the vegetable oil and granulated sugar.
Add the eggs and elderflower syrup and beat with an electric mixer at medium speed for one minute. Add the gluten-free flour blend, salt, baking powder, dairy-free milk, xanthan gum, and gluten-free vanilla extract; beat at medium speed for one minute until just combined.
Spoon the batter evenly into the cupcake liners. Bake for 18-20 minutes or until the centers spring back when touched and cupcakes are very lightly browned.
Let the cupcakes cool in the pan on a wire rack for five minutes. Remove cupcakes from the pan onto the rack and cool completely before frosting.
For the frosting: In a medium mixing bowl, beat together the softened butter and vanilla paste until smooth and creamy.
Gradually add the powdered sugar, one cup at a time, beating well after each addition. Alternate with 1 tablespoon of dairy-free milk and 1 tablespoon of elderflower syrup until all ingredients are blended and the frosting is smooth.
Beat in additional dairy-free milk if needed to obtain the desired consistency for frosting.