Cut the tomatoes into slices and place in a salad bowl.
Cut the cucumbers into strips and add them to the tomatoes.
Cut the mozzarella cheese into large wedges and add it to the vegetables.
Combine mustard, honey, vegetable oil and soy sauce in a bowl. Mix everything until smooth.
Heat a grill pan with vegetable oil. Season the tuna fillet with salt and pepper on both sides and place it on the grill. Fry the steak for 5 minutes on each side until golden brown, then let the fish rest for 5 minutes.
Add arugula to the bowl with the remaining ingredients.
Place the fish on top of the vegetables. Pour the dressing over the salad, add salt and pepper to taste. The dish is ready. Enjoy!