To make this Spanish Bar Cake gluten-free. Simply substitute the all-purpose flour. With a high-quality gluten-free flour blend. Make sure the blend you choose contains xanthan gum. Or add 1/2 teaspoon yourself. To mimic the binding properties of gluten. Ensure all other ingredients. Including the baking soda and powdered sugar. Are certified gluten-free. To avoid any cross-contamination. Follow the same steps. And you'll have a delicious, moist, and gluten-free Spanish Bar Cake. That everyone can enjoy. Without any worry.