Heat a drizzle of olive oil in a skillet over medium heat. Season the salmon fillets with salt and pepper, then cook for 4-5 minutes on each side until the salmon is fully cooked through and flakes easily with a fork. Set aside to cool slightly.

Prepare the sauce:

In a small bowl, mix the Greek yogurt, Dijon mustard, and lemon juice. Add salt and pepper to taste.

Assemble the sandwich:

Toast the whole-grain bread slices if desired.

Spread the yogurt-mustard sauce on the bottom slices of bread.

Place the cooked salmon fillets on the bread.

Add cucumber and red onion slices on top of the salmon.

Garnish with fresh dill.

Close the sandwich with the remaining bread slices.

Serve:

Cut the sandwich in half and serve immediately.

Enjoy your fresh and flavorful Salmon Sandwich!