Heat 6 tablespoons Hellmann's® or Best Foods® Real Mayonnaise in 12-inch nonstick skillet over medium heat and cook onion, stirring occasionally, until onion is tender, about 5 minutes. Stir in garlic and flour and cook, stirring constantly, 2 minutes. Stir in tuna and cook, stirring occasionally, until heated through, about 2 minutes. Whisk in broth. Bring to a boil over high heat. Reduce heat to low and simmer, stirring occasionally, until thickened, about 2 minutes .
Stir in bow ties, peas and cheese and cook, stirring occasionally, until heated through, about 2 minutes. Season, if desired, with salt and pepper. Turn into 2-quart shallow casserole.
Combine remaining 2 tablespoons Mayonnaise with cracker crumbs; sprinkle over casserole. Bake 20 minutes or until golden.