Healthy Chicken Tikka Masala

Name: Healthy Chicken Tikka Masala
Ingredients: 1/4 cup coarsely chopped fresh ginger (from a 3-inch piece); 1 cup coarsely chopped onion; 3 tablespoons coarsely chopped garlic (from 5 to 6 cloves); 1/2 cup plain yogurt (not Greek), plus more for serving; 1 1/2 pounds boneless, skinless chicken thighs; Kosher salt and freshly ground pepper; 1 tablespoon tandoori spice mix, such as Frontier; 3 tablespoons safflower oil; 1 cup pureed canned tomatoes (from a 14 1/2-ounce can); Warmed naan or flour tortillas, cucumber spears, and fresh herbs, such as cilantro and mint, for serving