Preheat the oven to 200 ° C (top / bottom heat, convection: 180 ° C). Cut the seitan into wafer-thin, approx. 3 cm long slices. Fry in hot oil for approx. 3 minutes on each side and season.
Bake the bread in the oven for 10 minutes. In the meantime, prepare the lettuce and vegetables, cut into small pieces and roughly cut the lettuce. Mix the soy yogurt, curry, paprika powder, tomato paste, mayonnaise, agave syrup, lemon juice and sea salt for the sauce.
Halve the bread horizontally and vertically and coat the inside with sauce. Put the salad on top. Spread the red cabbage, seitan, tomatoes, cucumber and onions on top. Drizzle with sauce, close and serve.