Healthier Chicken Tikka Masala with Cashews

Name: Healthier Chicken Tikka Masala with Cashews
Ingredients: 1 cup low-fat yogurt; 1 1/4 cups grated onion; Four 8-ounce skinless, boneless chicken breasts, pounded to an even thickness; Salt; Freshly ground black pepper; 1/4 cup raw cashews; 1/2 cup boiling water; 1 1/2 teaspoons grapeseed oil; 1 garlic clove, minced; 1 teaspoon grated fresh ginger; 1/2 jalapeño, minced; 1 1/2 teaspoons garam masala; 1 1/2 teaspoons tomato paste; One 14-ounce can crushed tomatoes; 1 teaspoon sugar; 1 1/2 teaspoon kosher salt; 2 tablespoons chopped cilantro leaves