Drain yogurt and grated cucumber in a cheesecloth-lined colander for several hours to prepare the Tzatziki Sauce.

Mix the drained yogurt and cucumber with garlic, grated onion, lemon juice, olive oil, dill, salt, and pepper. Chill the Tzatziki Sauce.

Cut the ciabatta roll in half horizontally.

Spread 1-2 tablespoons of Tzatziki Sauce on each half of the roll, adjusting to taste.

Layer the bottom half of the roll with lettuce, tomato slices, onion slices, artichoke hearts (if using), cucumber slices and thinly sliced black olives.

Press crumbled gorgonzola and parmesan cheese (if using) into the cut side of the top half of the roll.

Place the top half of the roll onto the layered bottom half, forming the sandwich.

Cut the assembled sandwich in half and serve immediately.