To make this Rich Kahlua Brownie Cake gluten-free. Simply substitute the all-purpose flour. With a 1:1 gluten-free flour blend. Make sure the blend contains xanthan gum. For proper structure. Or add 1/4 tsp separately if not. Since the other ingredients. Including the Kahlua, chocolate, and espresso. Are naturally gluten-free. The flavors will remain. Just as delicious. Your gluten-free guests. Will still get to enjoy all the rich, indulgent flavors of this coffee-infused treat!