Heat broiler. Spray broiler pan with nonstick cooking spray.
Heat oil in a nonstick skillet over medium heat. Add onions and 1/2 teaspoon of the steak seasoning. Cook for 10 minutes, stirring occasionally, until translucent and lightly browned.
While onions are cooking, season steaks with 3/4 teaspoon of the steak seasoning. Broil for 2 minutes per side. Remove from broiler and slice thin against the grain.
Place pizza crust on the broiler pan and spread with mustard. Sprinkle half of the cheddar and half of the provolone over the top, then add the sliced steak and onions. Sprinkle remaining cheeses over steak. Broil for 1 minute until cheese melts and steak is heated.
Remove to cutting board and cut into 6 slices.
490 calories; 23 g fat (10 g sat.); 34 g protein;
35 g carbohydrate; 3g fiber; 849 mg sodium; 79 mg cholesterol