Begin by boiling water in a medium saucepan. Once boiling, remove it from heat and submerge the vermicelli noodles for about 5-7 minutes until they're tender yet firm. Drain and cut them into 2-inch lengths; set aside to cool.

Fill a large, shallow bowl with warm water deep enough to fully submerge a rice paper sheet. Soak one sheet for about 10-15 seconds until pliable. Remove, let excess water drip, and place on a smooth, damp surface.

Lay the softened rice paper on your working surface. In the center, layer a small amount of vermicelli noodles, strips of tuna, cucumber, avocado, and red cabbage.

Gently fold the sides of the rice paper inward to protect the fillings and roll tightly from bottom up, being careful not to tear the rice paper. Repeat until all ingredients are used.

In a small bowl, whisk together soy sauce, rice wine vinegar, and sesame oil until well combined. Adjust flavors to taste.

Cut each rice paper roll in half diagonally and serve on a platter, garnished with sesame seeds and accompanied by the dipping sauce.