Gluten-Free, Vegan, and Vegetarian are on the menu, but the same kitchen also prepares what you avoid, so cross-contamination is possible. Tell staff what you react to, and ask how your dish is prepared before you order.
An organic burger restaurant in Salzburg's Linzergasse with its own gluten free menu. The site says gluten free food goes into a separate fryer, gluten free bread is cut with separate tools and toasted separately. The gluten free bun costs 2 EUR extra.