You can use different types of bread!
In a bowl, mix tuna, Greek yogurt, 1.5 tablespoons lemon juice, 1 tablespoon allulose, sweet corn, and pepper.
Place the heated bread, sliced in half, on plastic wrap and stack all the mixture on one side.
Top with julienned onion, julienned cucumber, sliced boiled egg, and halved cherry tomatoes.
In a bowl, combine 0.5 tablespoon whole grain mustard, 0.5 tablespoon allulose, and 0.5 tablespoon mayonnaise to make a sauce. Spread it on the other slice of bread, cover the sandwich, and wrap it up.