For the tofu club sandwich, finely grate lemon zest and squeeze 3 tbsp. juice. Mix with mustard, sugar and 5 tbsp. oil. Season with salt and pepper.
Cut tofu into 8 slices and let marinade for 3 hours.
Wash lettuce, slice tomatoes and onion. Remove tofu from marinade, save marinade.
Fry the tofu slices in 1 tablespoon oil until golden brown, keep warm in the oven. Toast slices of tofu. Heat remaining oil in a frying pan.
Crack eggs and fry for 3 minutes until whites are firm. Divide fried eggs among four toast slices and top with tomato slices.
Place one slice of toast on each, top with 2 slices of tofu, onions and lettuce and drizzle 1 tablespoon marinade. Spread ketchup and mayonnaise on the remaining slices of toast and finish by placing on top of the sandwiches.
Cut the tofu club sandwiches diagonally.