Heat oven to 350 degrees F. Coat large roasting pan with nonstick vegetable-oil cooking spray. Rub turkey on all sides with olive oil and lime juice.
Mix onion salt, chili powder, dried oregano, cumin, garlic powder, allspice and cayenne in small bowl. Rub 1-1/2 tablespoons mixture over turkey.
Roast turkey in 350 degree F oven for 1-1/2 to 2-1/2 hours or until internal temperature registers 165 degrees F on instant-read thermometer. Remove turkey to warm place; let stand 10 minutes.
Pour off all but 2 tablespoons drippings from roasting pan. Sprinkle flour and 1/2 teaspoon of remaining dry rub over bottom of roasting pan; cook over medium-high heat, scraping up any browned bits from bottom of pan, for about 1 minute. Gradually whisk in chicken broth until smooth; cook, stirring occasionally, until thickened, about 2 minutes. Strain gravy through sieve into gravy boat; keep warm.
Cut off each half of the turkey breast from the bone. Wrap one half; refrigerate for up to 3 days or freeze for up to 4 months to use later for Turkey Fried Rice. Slice other half of turkey breast and serve with the gravy, and mashed potatoes, if desired. Makes 6 servings.