Soak cashews in boiling water for 15 minutes. Crumble tofu into a blender.

Add soaked cashews, lemon juice, zest, and a pinch of salt to the blender. Blend until smooth and creamy. Chill for 30 minutes.

Slice red onion thinly and whisk olive oil, vinegar, sumac, lemon juice, and salt in a small bowl. Add onion slices to marinate for 10-15 minutes.

Slice tomatoes thickly and toss with olive oil, minced garlic, and herbs in a bowl. Allow to marinate for 5-10 minutes.

Spread tofu mixture on one slice of bread. Layer with marinated tomatoes, sumac onions, and avocado. Top with lettuce and another slice of bread. Press gently to close.

Slice sandwich in half and serve fresh with a salad or chips.