Place 2 sheets of dough on top of each other and form a kind of nest, brush with butter, place 1 red snapper fillet in the middle and pull up one edge with the dough protruding. Cut the avocado into slices. Spread the avocado and spinach between the batter and the fish. Brush again with butter and bake in the preheated oven at 180 ° C for about 8 to 10 minutes.
In the meantime, mix the ingredients for the sauce well. Pour the sauce over the cooked fish, tablespoon at a time.