Line a 13 x 9-inch baking dish with aluminum foil. Salt the bass and transfer it to the dish.
Mix the basting sauce by mixing the ketchup, Hellmann's® or Best Foods® Real Mayonnaise, olive oil, onion, brown sugar, mustard, Worcestershire sauce and vinegar in medium bowl. Pour the sauce over the bass and bake 20 minutes. Spoon sauce from bottom of baking dish over fish. Continue baking 20 minutes or until fish flakes easily with a fork.
Using metal spatulas, carefully remove bass to serving platter and garnish with lemon slices.