Preparing the tuna: Place the tuna cubes in a bowl.
Mixing the ingredients: In the bowl with the tuna, add the cucumber, mint, Greek yogurt, lemon juice and olive oil. Season with salt and pepper to taste. Mix gently to coat the tuna with all the ingredients.
Serving: Serve the tuna tartare very fresh, accompanied by cucumber slices for a crunchy texture. You can also present it with a cabbage salad for a touch of freshness.