Recipe Method

1. Mix onion, mayonnaise, tuna and mustard and season with salt and pepper. 
2. Spread butter on one side of each slice of bread. Place one slice at a time in jaffle iron, buttered side facing down. 
3. Spoon tuna mixture on top of bread. Add a slice of cheese before placing second slice of bread on top, buttered side facing up. 
4. Close iron and trim off excess bread. Fry over low heat for 2-3 minutes per side, or until golden brown. 
5. Remove from iron and make more jaffles with the rest of the bread and filling. 
6. Serve warm with cucumber slices.