Vegan Gyro Sandwich

Name: Vegan Gyro Sandwich
Ingredients: Sauce:; 1/2 large cucumber, peeled; 1 cup plain vegan yogurt; 1 tablespoon lemon juice; 1 teaspoon dried dill weed; 1 teaspoon dried chives; 1 teaspoon sucanat; 1/2 teaspoon salt; fresh ground black pepper to taste; Meat:; 1 tablespoon olive oil; 1/2 tablespoon minced garlic; 1 (16 ounce) package seitan; 1 teaspoon ground cumin; 1 teaspoon dried oregano; 1 teaspoon dried basil; 1/8 teaspoon ground cinnamon; 1/8 teaspoon ground nutmeg; 1/8 teaspoon chili powder; Sandwich:; 1 tomato, thinly sliced; 1 red onion, thinly sliced; 2 cups shredded lettuce; 6 pita bread rounds