To prepare this Spanish Bar Sheet Cake gluten-free, substitute the all-purpose flour with a 1:1 gluten-free baking flour blend that includes xanthan gum or similar binding agents. Ensure the caramel sauce used is certified gluten-free, as some commercial sauces may contain hidden gluten or cross-contaminated thickeners. The texture may be slightly more delicate, but the flavor remains rich and nostalgic.